My story is simple.
I always had lone, creative hobbies (beside astronomy). As a young kid, I built Lego stuff. From the age of 11 to 16/17, I did paper modelling Reinvented everything, I didn't have a clue then (no internet) that this is actually a quite popular hobby. Then I did programming, now I design Lego stuff again (Technic).
EDIT: I forgot music. I played the drums in a progressive metal band, that wasn't really a lone hobby. We wrote our own music.
I first met programming in elementary school, at the age of 13 or 14. It was only a small part of the computer science class, extremely basic stuff (maybe it was some Basic). I immediately had the sense of programming (the sense of the ability to create anything from zero, breaking down stuff to manageable pieces), but I only had a 386 then as I can recall, and didn't know how to do (compilers, editors etc) programming and I didn't bother too much with it.
The next time I met programming (C language) was in the University (19 y.o), programming class. It was only an introductory class, since it was a Mechanical engineer university. I immediately fell in love with programming and it became a "full-time" hobby. I learned on my own, I didn't have internet till 2009 when I immediately joined Gamedev.net. I learned things by downloading random tutorials to floppy disks, and learned by hacking a LOT.
I reached some level in programming but I didn't want to be a real programmer, so I didn't worry about gaining much knowledge. I was excited from coding, so didn't read any books besides documentation. I learned whatever I needed to work on specific projects which were always fun/dream projects, never did "big" projects for only learning.
Actually somehow I ended up rejecting programming jobs (again, I don't have a certificate). One of them from another country just found my portfolio on the web, another found me through a common friend, I also applied for 2 jobs just for the heck of it on a job fair, one of them would have hired me (passed their written exam and the interview), the other one was much about C++ knowledge which I don't have.
Somehow I'm lucky, or smart (...), but I never stressed myself about always learning, always doing useful things in every minute of my life. I live a quite relaxed life (you may say lazy), but I feel successful. I always had a relaxed learning/work tempo in large which was always enough. I don't have big life goals and schedule so I'm not worried if I'm just relaxing even for weeks, and I usually don't feel I'm wasting time with anything and I don't really know the feeling of regret. When I do feel it, I just change my life.
For this reason I care much about always having free time which I can spend with doing nothing, that was the reason I rejected two job offers. I could have done both of them, I had just enough time, but I know I would have burnt out quickly.
Besides this relaxing thing I can go frenzy about the things I do, sometimes I do coding/building/whatever for weeks without stopping or slowing down.
You can check some samples of stuff I did through the links in my signature.