“What is success?
To laugh often and much; to win the respect of intelligent people and the affection of
children; to earn the appreciation of honest critics and endure the betrayal of false
friends; to appreciate the beauty; to find the best in others; to leave the world a bit
better, whether by a healthy child, a garden patch Or a redeemed social condition; to
know even one life has breathed easier because you have lived. This is to have
succeeded!”
― Ralph Waldo Emerson

You beat me to it, lol. My personal favourite, and the one that sums it all up, is the last one. I believe that 'success' can be defined in that short sentence alone:

'to know even one life has breathed easier because you have lived.'