What keeps me writing

Celebrated my 72nd birthday the other day and realized 40 years had passed since I published my first short story. There were a number of years when I didn't write because I went back to work as a nurse to put children through college. Nursing is exhausting work. Once I retired, long before I was 65. I began writing again. One of the reasons I keep writing is because putting words on paper and watching characters change and grow better or worse makes me happy. I have had a number of friends who began writing. Some of them were much better than I am, but for some reason, there was nothing to keep them going. I'm throwing this out to my friends. What keeps you writing. Janet