Congratulations on your retirement! I retired (or semi-retired as I still manage a farm, etc.) at around 58 due to health and also I was self-employed and the business I was in was dropping off due to the funding drying up for what I did (school programs - living history). The bad part is that you are in that "in between zone" - too early to go on Medi-Care . . but if you have your health insurance covered, then you'll be fine.
Don't listen to those who say that they instantly liked their retirement - it's an adjustment for anybody. The nice thin is that you have the time to sit back and "take stock" of where you want to go next. I ended up with several new hobbies and it's nice as my wife is retired and we have more time to spend together. We still have one parent left and that takes up a lot of time for her care. At first, I felt guilty for sitting down and reading a book - I felt like I should be doing something "productive". You'll adjust just fine though . . . keep busy . . . there are lots of things to volunteer for where you can give a few hours a week to help others out.
The one thing about retirement is that you "learn to do more with less". I'm not speaking just about money . . . but you learn that it's more enjoyable to not worry so much about "material things' . . and you have the time to enjoy things more. Take some trips, see some things you've put off seeing, get in touch with those that you've just haven't had the time to visit or see for a long time . . . and it's alright to sit and enjoy another cup of coffee.
Good luck to you and enjoy the new chapter in your life . . . when one door closes . .. another opens.