SNG when down to 4 players

[Penguinfan]

This is where I have trouble and need some strategy help. It seems that the blinds are high enough that even the smallest mistake can put you at a big disadvantage. I don't like to tighten up just to limp into 3rd, but aggression at the wrong time can be fatal in these games. With the exception on the occasional really bad beat I almost always make it to the last 4, honestly, but I would say I only make the money half of those times. When I do get to 3 people I find it very easy to knock out someone else and get to heads up, it's just this 4-player action that has me beat right now.

Any help out there?