Remember that your feelings are normal for first year teachers. Most importantly, get help from colleagues and support staff when classroom management difficulties get you down. You are new. You are not a failure if you ask for help. But you might be if you don't.
Teaching is a highly demanding profession.
What they are remembering is their own school days, when they were sitting in the students' seats. It's much different from the front of the room. Be prepared for The Big Dip. Unfortunately, most teaching foundation classes and methods courses give the barest brush to classroom management. Pursue with zeal whatever your university does offer.