First, is easier said than done, is relax. If you don't, you don't enjoy the trip. Next, use your mirrors, a 5th wheel turns differently than a bumper pull, so use the spot mirrors going around corners. Find some empty parking lot somewhere (it will have lines painted for you already) and practice, practice, practice. Practice pulling straight, backing straight, jack knife (parallel) parking, all that stuff you did in driver's ed, but with a trailer.
And from what I've recently learned towing with a family (this also applies to the relaxing part), NEVER expect to leave on time, EVER! If you want to be on the road with everyone AIS, tell them you want to leave 2 hours before your actual departure time.
Lastly, HAVE FUN! That's why you bought it right? Take it low and slow until you are comfortable and your confidence is built. You WILL get to a point when pulling the best is second nature. Until then, take it easy. Arriving late is better than not arriving at all!