Life is too short to not really apply yourself in the things you choose to do - and if you're not doing your best, choose something else. Unfortunately I learned this lesson quite late in life.
I've been very inspired by Mandelbrot's life, lately. Reading "The fractalist", his memoir, it's possible to realize two things: 1) how incredibly resilient he and his family were; 2) how he worked from his own definition of success: the fact that he ended up achieving what most people define as undisputed success was almost incidental. He was, to use Joseph Campbell's words, following his bliss.
Mandelbrot was born in 1924. The Mandelbrot set was discovered in 1980. Of course he worked on important things before that, but having his major discovery in the mid 50s puts things in perspective.