Aggression is indeed a key element of tournament poker but like everyone else before me said it's dependent upon many other factors. Are the cards falling your way, are you're opponents loose or conservative, how is your table image?
Often in many tournaments it's not so much the cards you play or how aggressive you are as much as what
hands you lay down when you've got the right read of the circumstances.
Poker is an odd duck, you can't dominate every game you play, play 100 tournament games and if you're any good you'll cash in 10 and win "maybe" 1. Experience teaches skill, not only are you playing cards but in poker it's even more important that you're playing people, aggression is important but even more important is knowing when and how to be aggressive.
"Selective aggression" = knowing when and how
When you have a short stack you have to be more selective, when you have the chip lead you can be less selective and more aggressive using your chips as tools to divine what your opponents reactions mean.
Blind aggression = donkey Why push when the donkey will pull you? That's why they are called "donkeys" you hold the nutz and they are betting into you and you just know they will go all-in if you don't push them.
Play lot's of tournaments, use the force Ethan, develop your instincts, patience, experience and selective aggression, or as Kenny Rogers likes to say: "Ya gotta know when tohold'em and know when to fold'em."