Jack of all trades, master of none. Well, bass is the closest to anything I'd call "master," but still a long way to go...
For me, I had a couple of bouts with piano lessons, once in my single-digit years and once in my teens. Enough to understand how a piano works, not enough to play it in public or actually execute a piece of music. Saxophone was my main instrument in school, about 5th-10th grade, then I stopped playing to focus on drama club. Had a drum set I banged on awkwardly too. I got a bass in my late teens to fiddle with, never really learned it, then it got stolen and I didn't replace it. Working as a camp counselor during my college years I learned some basics on mandolin, and for the next 15 years or so, insofar as I played music at all, the mandolin was it. Campfire stuff and noodling, I didn't consider myself a real musician on it, but it was fun.
Finally got the itch to try bass again about six years ago (I was 38). I had a wife and children and bills to pay by then, so even the cheap money for a starter Ibanez Gio on CL seemed like a big investment. That motivated me to get up early to practice every morning (the Mrs. stipulated that this new hobby was NOT to cut into family time) and to be as serious about it as I could. Eventually got to the point that now I'm in two cover bands with a pretty steady stream of bar gigs.
Bass got me into guitar. I'm still a pretty mediocre guitarist, but I wanted a) to understand what the guitarists in my bands were doing and b) to write on it. But bass is clearly my #1.