Before you go in for a session, think of the last time, but not as in "that was scary", but "that was something to learn from". Think of what you did wrong, and don't go crazy about it, but analyze it. What step did you do incorrectly?
First off, a sim is there to make initial mistakes, no harm done with that. You have to CLEARLY look back at your previous session and analyze your way of making the error. Was it just plain nervousness? Then take your time and think again before executing something. There is (usually) no harm done in taking a second or three longer to push a button when that helps you to push the right one.
Don't overthink it, just focus on what you learned. After a hew dozen hours you'll look back and see you progressed a lot.
An Airbus is just as much a toy as is a Piper. There's pax in both, buttons in both, blue side needs to be up in both. Don't get overly stressed because it's a faster, heavier toy
BTW: A training captain I talked to once mentioned that he considers your first actual flight in the aircraft a successful one if you get the seat the way you want it. The rest will follow smoothly
