I never learned to ride a bike as kid. At age 33, I realized I was about to move to a city where biking is close to mandatory (Melbourne), so I sucked it up and went for a couple of one-on-one adult bike lessons. Despite a first lesson that was so painfully fumbling and awkward I almost gave up, I showed up once more and figured out the key: when you start to fall over to the left, steer to the left, and you will suddenly no longer be falling. Rinse and repeat. We did a little cruise around the neighborhood, and hey, I was biking! Although I did have my ceremonial first fall when I crashed into a bollard at the end of a bridge (at very slow speed, fortunately).
Then I started commuting to my new workplace by bike. 15 minutes, a nice and easy ride, mostly on bike paths separated from road traffic -- but it was still scary as hell initially, and I walked the route a few times, trying to figure out exactly what I'd need to do to cross every road and turn every corner. The first morning was freaky, but I still remember the feeling of adrenaline rush when I arrived at the office the first time: Whoo! I survived! And then on the way back later that day, my shoelace gets caught up in the gears and I do a slow-motion crash onto the bike path. No real damage, but my nerves were sufficiently shot that I had to walk the bike home and skip the next day. Two days later I was at it again.
Next I attempted to learn curb hopping. My spectacularly mistimed 2nd attempt saw the wheel hit the curb full on, so I flew head over heels and shredded one knee to bits on gravel. Turns out you can keep biking just fine with a bloody knee, it only starts to hurt once the blood gets a chance to congeal.
And now I commute by bike every single day, rain or shine, 0 or 40 degrees. I wouldn't give it up for the world and am considering upgrading from my current trusty but heavy mountain bike into a zippier road model.