Fear is an instinct and it has a good useful purpose, self preservation. While there are times when it might be a good idea to put on a brave face, there are situations when its best to save some time, turn tail and run. You can be disabled by fear, but more often a lot of good decisions are made based on fear; for example caveman running away in fear from T-Rex.
I know, I know, they didn't walk the earth at the same time. It was just put out as a vivid illustration (although there are those on this very site who would have you believe that they did infact co-exist just 4,000 short years ago).
