Mistakes will happen. It’s learning from them that’ll make you improve. Even the most experienced drivers drop a bollock now and then. If something doesnt look or feel right (I. E the trailer height) don’t just think it’ll be alright CHECK IT and DOUBLE CHECK IT. As for the days drive just treat it as a driving test /lesson. Good thorough check of the vehicle. Check the load security etc and drive like you were taught to do. Don’t be afraid to ask questions neither.