I was effectively "unschooled" from grade 3 until university. Apart from some effort being made to have me go through math workbooks, and a couple of distance-ed high-school courses, I was pretty well in charge of my own time. Bad things: Less friends, less socialization (not for lack of trying from my parents - there were enough other homeschooled kids around that we did group activities with, but I didn't like most of them very much). I didn't date, and that was very frustrating for me. Good things: You learn how to look stuff up for yourself instead of relying on someone to tell you.
This is around 8 years behind me now, so it's hard to judge whether it was a good thing or a bad thing. I think I've done okay since...
First, figure out a vague plan for what you want to do with your life. I don't mean you need to know right away, but you should have some idea of a direction (do you need a degree? apprenticeship? free-agent?). If you want, say, a degree, figure out which universities you want to go to. Find out what their policies are for special circumstances, and work towards fulfilling their requirements. I had to write the SATs to get into university, since I didn't have a highschool diploma. It's a normal thing to do in the US, but it's fairly unusual here in Canada.
The good news is that, outside of your career goals, you're free to study anything you like. Do you want to read about electronics & dream about building a Tesla coil? Now you can! Physics beyond Newton & dynamics? You can do that too. Don't care much for history? Screw it. If it doesn't relate to your goals, you can forget about it. The important thing is to keep those goals in mind, and to stay positive about your abilities. For years I told myself I was bad at math, so I didn't go to school for physics like I'd always dreamed of. Eventually I discovered that I was actually quite capable of understanding it, and the math I was bad at was better suited for a calculator anyways.
So I guess to summarize: Have some idea of your life goals and what you need to do to achieve them. Focus on those goals & the steps you need to take for them. Believe in yourself.
 I never did build one. At this point I'm wise enough to think that with my skill set, it's probably a bad idea. Plus, I have way too many computers & electronics around that I'd probably fry.
 Not that it's necessarily a good idea to do this, knowledge is always worthwhile, but it's not like you'll need it to get a job/be successful in life.
 I can only find basic derivatives/can't remember most strategies for finding an integral, but I know what these things are and why I'd want to do them, and since I don't need to do it on a regular basis, knowing about them is almost as valuable.