To give context: I'm 17 and just started college (web dev. with design degree). Got my first computer at 13. Have been interested in startups and designing/coding for a couple of years. Had a job at a web dev. company in Summer '09. They offered me a full-time job as a front-end designer for when I finished high school (Summer '10), but I gracefully declined as I wanted to pursue my own projects and go to college. Debated about going to college and eventually decided to go for the networking aspect - and since my country has a free educational system, it's not as if going would put me in debt like in the US.

But I have this ongoing problem. At first, I just thought I was bad at generating good startups ideas, but now I'm starting to think maybe the problem is over-thinking any ideas I have to the point where I can't see them succeeding. I have several (somewhat niche) ideas which I know I could turn into high-profit lifestyle businesses, but I want to go for something a little bigger than lifestyle since I'm prepared to put every second I have into it. Also because I have no family to support and don't need immediate income.

In the meantime I've just been improving my coding and learning more so I'm not exactly wasting time, but I'd like to get started on a real project with good potential.

Is this a common problem? I'd be hugely thankful if anybody could give some advice.