I just saw a great video by the astronaut Chris Hadfield, "What I learned from going blind in space":


Being in space is incredibly stressful. To overcome their fear, they train train train train, so that when something happens, it's not new, and they know what to do reflexively. It also has an element of what psychologists call "flooding", where you expose yourself to what you're afraid of until you realize that there's nothing to be afraid of.
- Benton