A good Poker player will change playing styles throughout a game, If I am low on chips I will tend to play passively, giving the lead to more aggressive players so they lose more chips to me when I hit a Monster hand.
When I get a bigger than average chip-stack I will then become more aggressive to pressurise shorter chip-stacks and take advantage to steal blinds.
Poker is a game of changing gears, knowing when to step on the gas, and when to ease off, It is finding the correct balance that makes you a good player.
When the fun Stops, STOP!