[impendia]

I disagree. OP is fifteen. I was staggeringly ambitious when I was fifteen, and although I didn't achieve everything I was aiming for, I'm super-glad I was.

It is easy to "change the world". Next time you're walking on the sidewalk, and see a piece of trash, stoop and pick it up. Presto: you've made the world a better place.

The question is how much, but certainly saying that OP "won't have any friends or girlfriend or normal life" IS COMPLETELY WRONG. Most very successful people I know have satisfying personal lives.

I dissent from the parent. I would suggest you not ask yourself "Are you willing to work harder than anybody, for 20 years?", or indeed to compare yourself to others at all. The question I would invite you to ask yourself, which it sounds like you are doing already, is "What is something interesting and helpful I could learn?"

Good luck to you!