Why is it so hard?

(I live in a third world country)

The main reason im in here is this: I've been going to the gym for 8 months, and recently came across someone, i'll admit it, i like her, i been speaking to her, recently got to hear her name, and last wednesday, during a conversation she told me her age, shes is 15 years old, why? Why does the first normal love that i had since school has to be like this? I can't just ignore the fact that she's underage, i can't "go for it" either, i'm 20.

In the country i live in, people do whatever they want in my situation, friends have told me to just stay as friends until she is 18, but i can't do that. It seems so simple to them.

Why is it so hard? All I've done is good, why does it seem so hard to live? Never did good in school, never at sports, videogames, love. I can't cope with all of this, i don't even know if the career i chose is what i like, but it seems so easy from outside, everything i look at is easy, friends have told me to just "relax" and let it flow, but what did that took me? I regret every minute from school, almost every interaction i had, i always end up like this, disappointment.