I retired @ 47 with DH who was 53. At that time my FIL moved in with us full time. My advise to you would be first, get fully rested! Most Americans are sleep deprived. Getting a full night of sleep will make everything go a little smoother.
Second, have a list of things you want to try. There have been a few 'new to me' techniques posted here - quilting with crayons & sharpie markers come to mind. Anyway make that list while you are still working. It will help.
Third, plan some fun. Go out for coffee with friends. Plan day trips. Don't get locked in your house. You will still need some human contact. They just won't be able to tell you to work weekends or stay late!
Fourth, leave some time for new adventures. DH became involved in local politics. I'm in a craft group & I teach a ladies Sunday School class. None of these things were in our retirement plans but they have been a great source of fulfillment. Also, plenty of places need volunteers! Now you will have the time.
Fifth, watch your outgoing cash. I don't mean be tight but unless you have mega bucks, plan your expenses. Do however, include some cash for pure fun!
Congratulations. Enjoy a new phase of life. Don't retire to nothing (or all day TV) but redefine life!