My opinion is something my parents told me.

'Life is not fair'

And its not that we shouldn't try to be fair, its just not going to end up fair, and that for me has always been an important understanding. I choose to be happy no matter what happens because I cannot control what happens (life is not fair), but I can control my reactions.

Unfortunately by thinking that life could be fair (instead of just being as fair as we can) people ultimately destine themselves to depression wishing things were the way they couldn't be.