Before going into this Discovery Channel shark-swimming trip in Tahiti, I thought I might have to change my wetsuit a few times.

People manifest fear by focusing on negative outcomes, says Rob Bell, a sport psychology coach and the author of No Fear: A Simple Guide to Mental Toughness.

You need to see past worst case-scenarios and "look at fear as a positive," he says. You can either look at fear as a threat or as an opportunity for something good to happen."

What follows are Bell's pointers.

1. Adjust your thinking

"Have an attitude of no regrets": Know that life isn't a dress rehearsal. If you want to do something, you'd better do it.

2. Find a coach

"Confidence is contagious": The best way to gain confidence is to see it in others. Let someone teach you what you need to do to banish the fear.

3. Build up to it

"Desensitize yourself to the fear": Proper education and gradual training will let you push past thresholds you previously couldn't even approach.

4. Face the fear

"Do it anyway": Repeatedly facing a fear is the ultimate way to overcome it completely and permanently. Avoiding a fear only allows it to build up.