[talliedthoughts]

Not only a hindsight measure, but also a very individual measure. Society usually defines success as some combination of wealth and fame, but everyone can choose another definition of success for themselves.

Say someone defines success for themselves as "becoming the number 1 basketball player in the world", then gets into the top 10 and becomes rich and famous because of it. They might internally consider themselves a failure, even though they are very successful in the eyes of everyone else.