I run. I climb. I spend time smiling in cold windy conditions. I also engineer stuff. I make simulations that are not half bad. I design stuff that no one else has ever thought of. I also try to balance my perfect life.
As I move ahead in life and approach the time where I don't have classes or the ability to take out more student loans it becomes more important to prioritize my life and fine that perfect balance. That is hard because at this point in my life my physical capabilities are on the upswing and I want to spend lots of time and energy focused on them so that I can run really fast and climb really hard and high. I am also an engineer and I measure my success by production. When I finish a simulation or a prototype I have something to show. I also like to be credited for what I produce. Which means that I want to make my living (and pay off my student loans) by producing something. So while I could try and do the professional athlete thing and eventually be successful I can't do it because I wouldn't really produce anything. I like telling people I ran a 32:58 10k but I also like telling them I created and built an ice axe from scratch.
The title of this post does not only relate to physical training but also the mental effort in life. To perform at a high level in anything you have to practice that activity many times. There are many failures, miscalculations, sore quads, invalid simulations, late nights, mistakes, and lapses of concentration on the way to the top.