Above anything else, always remind yourself of why it is that you play poker. Because you are a winning player! No matter how bad a session may get, your time is well spent at the tables because in the long run you are profitable.
A great way to constantly remind yourself of this is to simply set a HEM graph as the background on your desktop. See that line that goes up and to the right? That is why you can laugh about all the bad beats and coolers.
2) Keep sessions short
I generally don't like to play more than 3 hours at a time. I find that I tend to get hungry, bored or tired if I go beyond that. All of which can have a negative impact on my game. Your number of hours or hands might be more or less. Whats important is to know what it is and stick to it. The only time that you should play beyond it is when you are running well and the games are amazing.
3) Play earlier in the day
If possible play as soon as you wake up or after breakfast. I always find that I am at my best mental clarity earliest in the day.
4) Play less tables
As much as it sucks to cut back on tables you will tilt less and play better as a result. If you are running bad and playing a lot of tables at once, you are going to be hit with rapid fire bad beats and coolers. This is an obstacle for many live players trying out online who are used to 30 hands an hour. Understand that when you choose to play a lot of tables and you hit the doomswitch, its going to seem downright unbelievable at times. Hence all the rigged theories that continue to abound.
5) Use positive self talk
We are always talking to ourselves or making judgements about things or people whether we realize it or not. Controlling this inner stream of dialogue can go a long way to helping improve your mood and outlook at the poker tables and beyond. One of the first things that poker players should do is don't call them names.
Yes I know that (insert random expletive here) just hit his (insert random expletive here) gutshot again. That stupid (insert random expletive here)...STOP. What good is this doing? Poker is a game of decisions. He is making poor ones and will pay for it in the long run. Check his PTR real quick if you have any doubts. Take a deep breath and move on to the next hand now.
6) Stay focused
Remove as many distractions as possible. Don't let anything get between you and making the best possible decision in this hand right here and now. Even if it seems totally mundane like replying to that IM or text message. You are only going to be playing poker for a couple of hours at most. It can wait.
7) Don't look at your results
I realize this is a hard one for a lot of people. And I still struggle with it myself. Try to remind yourself that you can never play enough hands in one session to represent a statistically significant sample. So it is kind of crazy and totally pointless to keep checking the cashier every 10 minutes.