How do you get yourself to do a backhandspring on the beam when you do it on floor beams but your scared to do it on the high beam?

Answer 1

Increase the padding under the beam until it is a foot and a half or two under it, practice the move over and over until you are comfortable and accomplished enough that you feel safe and reasonably sure that you can complete the move most times without falling. Then remove layers of padding each time repeating the move until you are at the standard level of padding.

You are not afraid of performing the move just of falling ( or rather how bad it will hurt ), the more sure you are of your ability the less cautious you will be about failing.