Doesn't matter if you know how to fly a sim, because a sim doesn't slam you back against the seat when you takeoff, and a sim doesn't have 50+ lives in the back, and the sim doesn't have a reset button. The only way to get the confidence to do that is giving the controls to a primary student in a 172 and managing the fear that he's going to screw up with the need to let him learn. The mental process of constantly monitoring approaches and landings in a 172 without letting the guy kill you and himself is a huge confidence builder.

I don't think you're truly ever the "pilot in command" until you're first CFI checkride/training. Unless you've done it, you probably won't understand why.