Altering your play disguises the strength of your hand, and in some cases, you can make identical plays with two completely different holdings. This will confuse your opponent and make you unpredictable and difficult to play against.
It can even be profitable in these instances to be caught bluffing once in a while, or to show down an unexpected hand. It keeps opponents guessing and introduces an element of doubt into their game.
The next examples shows how you can "change" your game by playing totally different hands in precisely the same way, or by modifying your play based on slight changes in game dynamic.
Back to the hand: You decide to call and blinds fold. The flop is , your opponent bets 3/4 of the pot and you decide to call with your draw. The turn is the and again your opponent bets. You might consider a semi-bluff here. A raise on the turn usually means a very strong hand and it will be tough for MP2 to call unless he hold something good as well.
EXPLOITING POSITIONAll of the examples above involved hands that would be deemed "playable" pre-flop. However sometimes you don't even need this. All you need is good table position:
You are in the BB holding a trash hand like . Everybody folds to the SB who is a very careful player. He calls and the action is on you. He is unlikely to have a strong hand as he didn't raise so you can try to steal the pot. Just raise it up and force the SB to call a bet out of position.
You can't do this every time but it will work quite often.