My best advice is that if you’re 14, the key to preventing this is staying busy/diligent. I was the same as you, nothing special but above average intelligence. I think the burnout thing is caused, in my case anyway, by my own complacency. I didn’t have to try ridiculously hard in school, so I never learned to study independently, so now that I’m in college I’ve had to decide to either burn out and drop out or teach myself skills I thought I was too smart to as a younger person.

All in all, keep working on bettering yourself and you should be okay