When I was a teenager I borrowed a unicycle for the weekend from a friend at school. I practiced obsessively the whole weekend long and by Sunday afternoon I was able to go to the end of my street, turn around and come back. That Monday I returned the unicycle to my friend and never rode one again.

Later in life I made a concerted effort to learn how to manual a bicycle, and after a couple seasons of regular practice I gave up, I never really got the knack for it.