A few I can think of off the top of my head...
When things are frustrating or not going well, I always say, "Just put it in the Life's to Short category", then walk away from it for a while.
Another is my signature line, "If you obey all the rules, you miss all the fun", quote from Katherine Hepburn.
And finally, "If you can't stand the heat in the kitchen, put down your spoon". (for those who like to stir up trouble and then say "who me?"). :-)