There are a few things to take into account at this level.
1) You don't have any implied odds at all. You can't make speculative plays anymore.
2) Three-bets tend to become pushes all-in. If your opponent is raising too frequently, you can exploit this by shoving over his raises with just about any two cards. You generally don't want to do this deeper than about 27BB, though. It's very good around 20BB.
3) Winning small pots becomes more important. You want to stab at them, and if your opponent is letting you take them away, then you've found a big edge.
4) Proper short-stack strategy becomes very important.
You shouldn't be at all concerned with waiting for a bigger edge at this stage in the game. If you've found a strategy that you know gives you an edge, you should use it.
