When I was in basic training in the United States Army, we had to do what they called the confidence course. It involved climbing a ladder up to a 30 foot platform, and I do mean climb, because we quite literally had to climb to each rung. Once on the platform we had to repel down a 30 foot wall. Then we had to side step across a ladder made of rope going from a 15 foot tower to a 20 foot platform or catwalk, then lay down on a single rope and pull ourselves back down to the 15 foot platform. Then we had to turn back around and walk up a third type of rope (walk on a single rope while hanging on to two ropes) to the 20 foot catwalk. From the catwalk we had to climb back up a wooden ladder to the 30 foot platform. From there we had to climb down a 30 foot wall by way of rope webbing.
I don’t regret having done this in the least. I was terrified at the time, but I did it. And, now, each time I lack confidence, I think back to that accomplishment. Suddenly, my lack of confidence goes away.