People need to recognize that life can be unfair, that accidents will happen. None of this is to say that people have to acquiesce to the threats of life, to lie down and not attempt to change anything. There is nothing wrong with positive thinking and the hope that today will go well or that people might repent and treat others better. But (you) should not be shocked and angered when something does go wrong… cultivate the attitude that life is something to work at and that problems are normal. Learning to laugh at normal failures and irritations has been shown to be effective in defusing anger.
Mark Cosgrove, Counseling for Anger