Yeah, this may seem very counter intuitive, but I've seen it enough to know it's real.
What I mean by this is that sometimes your play can be so good that you step back mentally from the game, and think, "how did I do that?"
This can happen two ways.
1) You get out of a situation that seems to be certain death. This is probably the worst. Because it's almost certain to shake you out of your focus like someone just slapped you in the face. In some ways you would have been better being killed in that situation because at least your focus remains in tact.
2) The other type is more the slow burn type. You slowly but surely are making a fantastic run on a game only to realize late in the game that you are making an amazing run. With this, the problem of "How did I do that" is that self doubt can creep in. You also might play dangerously conservative to the point that you are no longer playing a game you are used to, and the conservative game you are playing actually is killing off more men. With this, the best bet to just to focus one board at a time. Easier said than done though.