I think I'm the opposite of people here. I started working as a web designer in high school and eventually moved on to owning my own company and being self-employed. At some point I had like 15 employees working under me. At some point I wondered if I'd ever finish college, because I was making tons of money without it. I traveled overseas every year (sometimes twice!) and took vacations whenever I wanted, ate at expensive restaurants, bought nice things, etc.
But I never intended to be a designer forever, it was a high school internship that turned into a career, and that made me miserable. I came to hate web design, and became more irritated every time I'd see professional artwork that was shittier than mine, because what was stopping me was the fact that I knew I was missing some crucial skills, and didn't know where to find them.
And really, that's it. It wasn't that I ever failed as an artist-- I'd never actually tried. So right now I've quit my "career," and am using the rest of my money to get an Illustration degree. Finishing out my degree after having worked since high school changes the perspective for me. On one hand we do a lot of work (my illustration program is really career-focused and teaches entrepreneurial sensibilities and beats the everliving s**t out of us due to the sheer workload), and while it's physically and mentally taxing, it's nice to be back in school after having worked, handled clients, having dealt with law suits, and taxes, etc. I'm getting all the info I was missing to change careers, and my instructors are great mentors that have really helped my sensibilities. I've had more than one instructor say something to the effect of "Oh my god, you should have come sooner!"
After the first semester there-- actually, no. After my first WEEK there it was clear how much I'd outgrown my junior college and didn't even realize it, once I was instructed by people who made work that was closer to what I was making in my spare time. Not saying my JC sucked, because my JC actually taught really strong fundamentals that make my life easier. It's just... they were all studio painters, and I never was. They couldn't tell me how to reach my goals because it wasn't their area of expertise. Now I have lots teachers who have actually made things out in the world that I actually knew about before getting to study under them: gaming, animation, editorial illustration, comics, etc. Last semester, my illustration teacher told me that I draw better than he does. It was ******** unreal. Doors are starting to open. I'm getting recommended for work/internships/etc.
I tend to think I'm thriving because I know what I wanted from art school. At age 18, I wasn't too clear about that. In fact, I see plenty of 18 year olds who aren't ready. They shouldn't be there yet. I've learned that that's okay, too.
Anyway, I didn't post to be contrary or anything, I just wanted to throw my experience out there, in order to point out that being honest with myself would have made the whole process less agonizing (I was afraid to take the risk, even though deep down I knew there was a chance). I also don't want to insinuate that I think my future is guaranteed. It never is-- I have other job skills to fall back on, and I know I'm not wasting my time at art school because I came there with a purpose.
Oh, and the biggest thing I wanted to point out was that my 17-year-old self didn't know jack s**t, and that it was idiotic to base my future on her decisions. Also, (this is a point that other people have made in this thread, but in the other direction, really), making the decision to turn away from professional art is the same as making the decision to turn towards it, in that you have the freedom to change your mind in life, as long as you're honest about what you can/will do. I think the biggest thing to take away from this thread in general is that you're never really stuck, whether that be chasing after goals or deciding to stop.