When we become more fearful with time, even though we succeeded the first time

When my son was two, we went to the swimming pool, where he would walk up on the 3 meter high diving board, jump into the water below, swim to the edge of the pool, climb out of the water, climb the stairs to the diving board, wait in line till it was his turn, and then go again. All by himself. I just stood at the side of the pool watching, ready to jump in, should something happen to him.

It was incredible to watch. There was absolutely no fear. At one point his arm floats fell off as he hit the water, and a lady helped him out before I could get in. Then he learned to hold his arms down when falling so that wouldn't happen again.

A year or two later we went to the same pool. This time, he was afraid to even jump from the 1 meter diving board. He never made a single jump.

As time goes on, we get more fearful, even when we were successful the first time! Why is that?

I've noticed it myself. In the beginning when I was doing head stand in yoga, I just threw myself into it, and I'd fall backwards all the time. Three times, four times. It would suck, but I wasn't really afraid of it. Now I'm able to stay in the posture for a fairly long time, but I'm so scared of falling over backwards that I overcompensate by leaning a bit forward and tightening all my muscles to I get really tired.

Why?

Last year I applied for a visa to the US and got rejected three times. Now I'm scared of even applying for a visa to India. Yes, I was unsuccessful, but no real harm was done, yet I'm still afraid.

Why?

The first few times, we seem to throw ourselves into it, fearlessly. Then we get set, and then fear sets in, and we dare not do it again.

Is it a form of sanding up? Rusting? That when there's not movement, we have to push ourselves out of the position we're in to gain momentum? Is it our unconscious mind that starts playing back all the things that could have gone wrong, and then builds up fear?

I've read that fear builds up in response to pain. If we get burnt on the stove, we establish fear of hot stoves as a way to protect ourselves. But in this case, there was only very limited pain to begin with. So why?

I don't know, but I'd like to know. Have you experienced this?