Fate
Do you believe in fate ?
Everyone knows what fate is, and the concept, as applied to your life is a bet you cannot lose, à la Pascal's wager.
My belief in it means that unfortunate events are easy to deal with, and allows me to stay calm and objective in the face of these events.
It's a shame that it happened, but it was meant to be. – me, all the time
On the other hand, if the event in question was a positive one, then what do you have to worry about ?
If at some point I receive irrefutable proof that fate doesn't exist, then my wholehearted belief in it has meant that difficult events throughout my life have been easier to deal with, as I felt they were out of my control.
If fate does exist, then I am correct, and have nothing to worry about.