Anticipating a child leaving home is stressful, so be kind to yourself. And anticipate that your child might be excited one minute and concerned the next. There are two people to take care of here: you, and your child. Helping him or her to be prepared might make you feel better too. (To keep things simple, I'll use "he" or "him", but I mean either.)
There are some basic things your young person needs to know.
By now I hope you have taught him how anticipate and navigate lifes' thornier issues: good work habits, drugs and alcohol, safe sex practices, etc. These are values and practices he has to develop and use on his own.
One other thing: letting go a little at a time is good for you and your son. You’ll both be ok.