Life is not a parabolic curve, nor does it go straight up. There are a lot of lumps, a lot of bumps. I have never yet met a successful person who hasn’t had to overcome either a little or a lot of adversity in his or her life. Overnight success is much more of a myth than reality.

Remember the four-minute mile? Humans had been trying to do it for centuries, since the days of the ancient Greeks. Historians found old records detailing how the Greeks tried to accomplish this. They had wild animals chase the runners, hoping that would make them run faster, among other measures. Nothing worked.

So, the experts decided it was physiologically impossible for a human being to run a mile in four minutes. Our bone structure is all wrong. Our wind resistance is too great. Humans have inadequate lung power. There were a million reasons -- until one day a human being proved the doctors, the trainers and the athletes all wrong.

In 1954, Roger Bannister showed the world that it could be done. Over the next few years, more and more people broke the four-minute mile once they realized that yes, it was possible.

When Bannister passed away this month, it brought back a lot of memories from that time in history that I remember so well.

The world was changing a great deal. People around the world were overcoming the long-perceived physical boundaries of nature. American pilot Chuck Yeager broke the sound barrier in 1947. And who can forget Sir Edmund Hillary and his Sherpa guide, Tenzing Norgay, conquering Mount Everest in 1953?

Many famous people have overcome tremendous adversity to triumph:

-- Bill Gates, co-founder of Microsoft and one of the richest people in the world, dropped out of school and had his first business fail.

-- Oprah Winfrey overcame terrible poverty growing up in rural Mississippi to become a billionaire media mogul who has inspired millions around the world.

-- According to some sources, Albert Einstein didn’t speak until he was 4 years old, and couldn’t get a job in physics for two years after graduation.

-- Richard Branson didn’t let his dyslexia stop him from founding Virgin Group and controlling more than 400 companies.

-- Popular recording star Jay-Z came from a rough Brooklyn neighborhood, but couldn’t get signed to any record labels as a rapper. In 2013, Time magazine ranked him as one of the most influential people in the world.

-- Vincent van Gogh is considered one of the greatest painters of all time, yet he only sold one painting during his lifetime.

-- Simon Cowell, star judge from “American Idol” and “The X Factor,” had a record company fail.

Botanists say trees need the powerful March winds to flex their trunks and main branches, so that the sap is drawn up to nourish the budding leaves. Perhaps people need to meet the stresses of life in the same way, though we dislike enduring them. A stormy period in our lives can be a prelude to a new spring of life and health, success and happiness. That is, if we keep our self-confidence and faith in the future.

Everyone faces adversity, pain, loss and suffering in life. When you go through those periods, it’s hard to remember that the emotions you’re feeling are only temporary. The best thing to do is to develop a plan for what you will do when these times hit and find your way to the silver lining -- the place where you can feel hopeful again.

You need a personal sense of commitment, the ability to let go when appropriate and strong values. Take charge of the things you can control, such as your treatment of others, the way you spend your time outside of work, how you think about yourself, how often you exercise, when and how to share your feelings, how to let others know you’re stressed and how mature you act.

Who says that you can’t accomplish your goals? Who says that you’re not tougher, better, smarter, harder-working and more able than your competition? It doesn’t matter if they say you can’t do it. The only thing that matters is if you say it. So, we all know, if we believe in ourselves, there’s hardly anything that we can’t accomplish.

Mackay’s Moral: How you handle adversity says a lot about how you will handle success.

The popular movie “Darkest Hour” has brought a lot of attention to former British Prime Minister Winston Churchill. It’s also brought a lot of attention to Gary Oldman, who won the Best Actor Oscar for his portrayal of Churchill.

According to biographers, Churchill did not have the happiest of childhoods. Neglected by his uninterested parents, he was sent to boarding school at a young age where he would write letter after letter pleading for his parents to visit him. Most of his requests went unanswered, and he ended up spending a succession of holidays alone at school without even the company of classmates.

Churchill would go on to suffer many failures both at school and in his political life, failures that would have defeated most people. But Churchill kept persevering, overcoming great odds and eventually leading his country through its most difficult times.

How did a man with such a difficult upbringing and spotty professional record achieve such greatness?

The answer may lie in the following story: Churchill was asked to deliver a speech at Harrow, the boarding school he attended as a boy. “Never give up! Never give up!! Never, never, never-never-never-never!” he roared.

What a tremendous lesson in perseverance!

Perseverance separates the winners from the losers. Those who persevere understand that luck is something only failures believe in. Perseverance has other names -- persistence, determination, a can-do attitude. Success in life depends on your willingness to never give up, even when the reward is delayed.

One of my guilty pleasures is that I occasionally stop at McDonald’s for a hamburger and a caramel sundae. The phenomenal success of the Golden Arches franchise is evident throughout the world. How was such a dynasty built? Why is Ronald McDonald a household name? The answer rests in the motto adopted by its founder, Ray Kroc. It simply reads, “Press On.”

As U.S. President Calvin Coolidge said: “Nothing in the world can take the place of persistence. Talent will not; nothing is more common than unsuccessful people with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent.”

In my line of work -- sales -- persistence takes on a special meaning. Somewhere between throwing in the towel and being a pest, you might find wisdom in this Code of Persistence for salespeople, developed by Herman Sherman. Resolve to:

Never give up so long as you know you are right.

Believe all things will work out if you hang on until the end.

Remain courageous and confident when the odds turn against you.

Never permit anyone to intimidate you or shake your belief in yourself.

Fight to overcome any physical handicaps and setbacks.

Try again and again, and yet again, to reach your dreams.

Take new faith and resolve from the knowledge that many successful men and women have had to fight defeat and adversity to achieve their greatness.

A few generations ago, Susan B. Anthony was both a revered and despised political figure. In the late 1800s, she tirelessly fought for a woman’s right to vote, a law that was not enacted until several years after her death. American women have been able to vote only since 1920.

At that time, the majority opinion was that women need not vote or be equal to men, and that anyone trying to change the status quo was simply a troublemaker. Still, Anthony soldiered on, and eventually earned a tremendous following. At a reception given in honor of her work, she was inundated with bouquets of flowers. Recalling her early years in politics, she commented, “They threw things at me then -- and they were not roses.”

Shortly before her death, she was asked if she was happy about how her life had played out. She said yes, she would do it all over again. “The spirit is willing yet; I feel the same desire to do the work, but the flesh is weak. It’s too bad that our bodies wear out while our interests are just as strong as ever.”

Susan B. Anthony serves as an inspiration that one person can accomplish greatness through perseverance.

Mackay’s Moral: Triumph is just the “ump” beyond “try.”

Other ministers told funnier jokes than Billy Graham, did a better job of illustrating Bible passages and organizing sermons, but no one was more effective than Graham in getting people to step forward in front of the congregation and make a commitment.

Translated from evangelism, that is what I call closing the sale. It’s no wonder, since he started his career as a Fuller Brush salesman.

The Billy Graham Evangelistic Association (BGEA), which was headquartered in Minneapolis, was instrumental in helping me get started in the envelope manufacturing business in the 1960s. No one I’ve ever done business with has cared about me the way the Billy Graham organization did. And I’m Jewish. They were one of the largest envelope users in the country and one of my biggest customers until they moved their headquarters to North Carolina 40 years later.

The BGEA earned loyalty that no amount of money could buy. They recognized a bedrock business principle: If you expect the other person to care about you, show that you care about them. It’s the Golden Rule of business. Because of this relationship, the BGEA got the best quality, the best delivery and the best prices. They paid promptly, many times before I even shipped the product -- absolutely unheard of in the envelope business.

No wonder I was proud to call Billy Graham a friend. Billy even honored me by providing an endorsement for my first book, “Swim With the Sharks Without Being Eaten Alive.”

Graham’s personal qualities set him far apart from other evangelists. He was a man of utmost integrity and concern for people. He was always quick to point out that he was just one member of a team.

How true! Billy was the quintessential Mr. Outside. He embodied the image of the organization, both to the outside world and to the people who work at BGEA. The late George Wilson was Mr. Inside at the organization. George passed away in 1999, and I was privileged to be asked to eulogize George, along with Billy. While Billy provided the inspiration for the BGEA, George kept the place humming. As Mr. Inside, George was low-profile, low-key and tireless, with an eye for talent and detail.

Most organizations need both these talents -- the salesperson who brings in the business and the manager who knows what to do with it. Surprisingly, many businesses don’t understand this -- and they also fail to realize those two talents seldom are found in the same person.

Selling is not a function of grandiose personalities and paraphernalia.

For decades, Billy Graham was on a list of the 10 most respected Americans. He maintained his status and high visibility by sticking to the qualities that got him there -- sincerity and moral integrity. While others in his profession succumbed to the “holy wars,” Graham kept getting stronger because he was a class act.

One of the stories that I think illustrates the real Billy Graham involved an incident that occurred while he was at a dinner with some staff members. When the server recognized Billy, she dropped her tray, scattering dishes all over the place. Graham immediately leaped up and helped her clean up the mess.

This was a perfect example of the humanity for which he was so famous. How many of us would reach out to another person and help her through such an embarrassing moment? Billy Graham’s act defined good manners and consideration for the feelings of others.

Networking is one of my passions, and there were few better at networking than Billy Graham. Networking is not necessarily a numbers game. The idea is not to see how many people you can meet; the idea is to compile a list of people you can count on.

When you encountered Billy at a function, he made you feel like you were the most important person in the room. He made eye contact and kept it. He smiled. He listened. He asked questions or made comments that showed he was interested in what you had to say.

Whether or not you agreed with his message, there was no question that Billy Graham was an icon for all that is good and right in this world.

Mackay’s Moral: Billy Graham was a master communicator, but more than that, a master of humanity.