"You practice every time you play your instrument"
Thelonius Monk is the man.
I bashed away at my dad's guitar as a kid, and my uncle bought me a 1/2 sized acosutic as a kid, but really I didn't do more than just bang on it. I must have been 15 when I first began seriously playing, the winter of my freshman year in high school.
It was kind of funny, actually. I'd taken a "guitar" class in 8th grade, basically a two-month music class where we were supposed to learn how to play guitar as an introduction to music (it was some sort of rotating "exploratory" thing so we'd be exposed to a lot of different "extracurricular" classes, with things like gym, wood shop, etc). It was actually only supposed to be a one-month class, but due to a scheduling glitch my class got stuck there for two straight classes. I was horrible - I was easily the worst guitarist in the class.
Then, six months later, I picked up my dad's guitar and something clicked. A few years down the road, after I'd gotten heavily into more "lead" gutiar stuff (I was a big punk rock/Nirvana fan when I was first learning), I ended up jamming with the guy who had taught that class. I was gigging semi-regularly with one of the substitute teachers in the same school district (he was my brother's soccer coach, and we'd played a few songs together at a pasta party where they'd carb-load and watch Braveheart before games), and Tom invited me down to play a couple songs with him at some sort of a school function he was playing at, right at the end of the school year. I chatted with the guy I'd taken that class with, then plugged in and started playing, and he just looked at me like "...what the hell happened to you
???!!" It was a pretty cool moment, and I think he was happy to see that, against all odds, he'd had a pretty big influence on me after all.