If you're ever feeling upset or disappointed that something didn't go as you wished just remember that it's only one day and one time. No matter what it is, you can always fix it or find another chance. 

Like if I have a bad hair day I try not to care because the next day I can do something different.

Or if I didn't get into the play I auditioned for there would always be other plays.

This can really go towards any situation . If you think that your situation is un-fixable or so horrible your world is going to end: just tell the truth and change your attitude about the future.