I've been enjoying doing some (indoor) climbing recently. It tickles the same problem solving/figuring out a challenge part of my brain that parkour satisfies. I enjoyed this article on the strange brain of Alex Honnold, one of the current greats of climbing:
One of the things I found really interesting is the way he seems to have just gotten used to fear through exposure. This is something that, again, I find in common between climbing and parkour. The more you expose yourself to situations that you find scary, the better you are at dealing with them. The fun part is that it spreads to situations that you haven't exactly encountered before, but are just similar enough that your brain can deal with them in the same way. A broad experience of different situations can set you up to deal with fear in many different ways.