Where did my golf swing go and how do I get it back?

We've all done it. When playing a good or great round, we lose it. Whether we can't hit the driver or whether it's shanking irons, we've all had those rounds where all of the sudden, without warning, our golf swing goes...somewhere. Why? Where does our golf game go and why did it leave?
Well, it's not gone anywhere. it's there. Just buried beneath the weight of all those things inside our head. Clearly if we had the physical ability to 'do it' right for 14 holes, we should be able to finish out the round with it. Right?