At krav we're always harping on about the fact that the way you train is the way you'll fight. That's because when your body experiences an adrenaline surge & your life is in danger, your brain & fine motor skills degrade, and your body automatically does what its been taught to do. So if you practice throwing weak knees to your partner, then drop your hands & stand there saying, "okay, your turn", that's what you'll do when the heat is on. Yes, its really true.
And here's a link to an article called Combat Psychology and Sports Performance that explains exactly why. You're welcome!