DEAR ABBY: I retired last year after 35 years of teaching. The one thing my students gave me that meant more than anything else: a note expressing appreciation for whatever I had done to help them during that year. Those cards and letters are more precious to me as time goes by. Rereading them, I recall sweet faces, special things about those kids, and the wonderful times we had together. They are priceless. -- KAY FRIEDRICH, ATHENS, GA.