Success to me is being able to look back on a day and think "I've accomplished something today, I've learned something today, I helped someone today, I wrote today." If I can say all that, it was a good day and I would feel successful.
I'm not very good at what most people use to define "success". I don't get the whole concept of striving for a big pay check, a new car every four years and a house bigger than I need. That just doesn't mean anything at all to me.
My children are productive, generally content, responsive citizens. That's success as a parent. My mother is comfortable and slowly regaining her faculties after a major surgery and a stroke because I am here to care for her. That's success to me.
I generally am content with my life. That's success. I have no big regrets. If I died tomorrow my only concern would be who would take care of my mother. My children are on their own. I'm not leaving a mountain of debt. Granted I don't own anything worth passing on, except my unpublished manuscripts, but what good are "things" since you can't take them with you. I think I've done a fairly good job with my life, considering the cards I was dealt. I consider myself to be a human success.