Just a quick thought...
Even if you play "perfect" poker during a poker tournament, the fact is that often the cards just run against you.
Sometimes that means that you go card dead. But, as noted in a previous post, there are ways to try to counter that awful situation.
The more frustrating way to me is when you play great but run into situations where your edges just don't pan out. Usually, I have found that I can handle one bad outcome, but two are tough too overcome and three are usually fatal.
For example, if you are playing great, raise with pocket Aces and a player moves all-in with A-K suited. If your opponent beats you with a flush, well, your stack will probably take a 25-50% hit (it depends on stack sizes, but I am assuming you are beating your opponents up to this point and building your stack.)
If you lose another tough one, like JJ against 99 (as I did recently), a few hands later, well, your stack is going to be nearly crippled or you will be out.
If you are crippled, you will be moving in with a big range of hands and hoping for the best.
The net of this is the following: It was just not meant to be. You can play great or even "perfect" poker, but the poker gods may be against you that day. I guess that's poker.
Note: I don't know how to define "perfect" poker. Phil says that he would win every tournament if it wasn't for luck. But, the other day at the WSOP, I read that Phil Hellmuth limped under the gun with pocket Queens and got upset when his opponent beat him with two random cards (a hand he would fold against a raise). So, if Phil is perfect, wh no raise?:-)