To me, being successful means...
Being able to take pride in what you've made of your life.

My definition of success has changed over time. 
Although the core of my own idea of success hasn't changed, it has been a difficult and continuing struggle to keep my sense of accomplishment separate from parental expectations. You'd think at 40 it would be easier to look your parents in the eye and not be sorry for having chosen a path that doesn't involve marrying a person wealthy by inheritance or profession in order to secure a pampered and indolent life for oneself and one's offspring, but...in my experience, parents don't change. I had to build yourself the protective space I needed to keep myself from wishing I had never been born.