You find out what you actually believe the first time it costs you something to believe it.

Beliefs are cheap until there is a bill. Saying you would never lie, never leave a friend out, never take the easy money, is free right up to the moment it would cost you a place on the team, a friendship, or money you actually need. That is when you learn which of your convictions were real and which were decorations. Most people are surprised at least once.

Look back at the last time something cost you to hold. What did you do? Then pick one belief you have never had to pay for, and decide the price now, before the situation turns up.