Tournament poker is definitely a different beast than cash games. You need to have a lot of patience and endurance. The blinds keep going up, so you have to stay sharp and not get frustrated. I've found that it's all about managing your energy, both mentally and physically.
Taking breaks is key. Stepping away from the table, even for a few minutes, helps you clear your head. Also, it's easy to get on tilt after a bad beat. You have to remember that variance is part of the game. Just focus on making the best decision every single hand, and the results will take care of themselves in the long run