I am living proof that you definitely CAN forget how to ride a bike. I learned when I was a kid, but I never rode much on my own; my dad and I would go out on the tandem often, but that didn't teach me balance, steering, etc. As an adult, I got a bike and found out that I didn't really remember any of it, and I pretty much had to learn again.

The advice you've gotten so far has been great- don't push yourself to try things you're not ready for, and enjoy whichever bike you're riding.