I got my first bike at 4...learned to ride w/o training wheels a couple weeks after that. My old man has always been the "tough love" sort...he refused to get training wheels on my first bike, he figured I'd learn if I wanted to ride bad enough.
Fast forward many years...I've never stopped riding since being a kid, but I definitely got more serious about it 5 years ago. I entered a XC mtb race on a whim, finished near the back of the field, and have been hooked ever since. I've since improved a lot and have done well in racing, but still have the drive to improve.
Things I've learned in that time were:
How structured training works. I used to just ride as hard as I could all the time, now higher-intensity stuff is just a small part of the riding I do. It's easy to want to go out for a ride when you aren't burnt out from the previous ride. Even if you aren't racing, it's not a bad idea to vary the intensity of your rides...if nothing else, it keeps things interesting.
Nutrition is key...I've done my share of bonking over the years. Being able to eat enough during the ride, has always been a struggle for me. This year I've finally worked on a fueling strategy that works for me.
Strava...don't take it too seriously. I enjoy battling over segments, but only when it fits my goals for that day's ride. Mostly it's a way to track what I've been doing, I don't even publicly post all of my rides/workouts. I often don't post the stuff that I consider "boring" like strength training, indoor trainer rides, etc.