Admit to Your Stupidity

Be honest with yourself.
When you are furious because some idiot sucked out a two outer on the river to lay a massive bad-beat on you, remember that you have made dumb plays and sucked out on others.
Everyone sucks out now and then.
Admit it.
Shrug it off.
Don't get mad.
If you can't admit it, you are not being honest with yourself.
You must be honest with yourself.
When you make a bad call, say to yourself "I'm making a bad call here - I shouldn't be doing this."
This makes it easier to throw the hand away when you miss because you already know you've made a mistake. When you hit you should say "Gee, that's lucky" and don't for a second think skill had anything to do with it.
When someone sucks out on you, imagine that you have just made a deposit in the "Luck Bank" - sooner or later you will withdraw that amount when you suck out on someone else.
Over time the balance in the Luck Bank always will go back to zero.
And that's just the way it is - luck is a zero-sum thing.