[Ghazban]

Nobody with a good A game stays on their A game all the time. If your B game and C game (and D, E, etc.) are profitable, you will still be +EV at the table. If you can only beat a given game when you are playing your absolute best, it probably should not be your main game.

To identify when things are off, you need to figure out what about your game is most likely to slip and be vigilant in looking for instances of it. For example, if your leak is that you call too much when your game is off, you should reexamine every call you make in the game to ensure its made for sound reasons and not because you're getting lazy and just want to see what the guy has.