Do you stress out a lot? Stop it! Seriously; just don't.
You know all those things that are on your mind, constantly? Let them go; release yourself to a life of freedom from the heaviness of unnecessary stress. If someone wronged you six months ago, the only person you're hurting by not letting go, is yourself.
If you made a mistake yesterday, forgive yourself for being human and move forward. Above all else remember that everything will work out.
If all else fails, have a cupcake! ;-)