I "retired" at 56 and found the first year to be very difficult emotionally (I'm about to turn 58). If I had to do it over again, I would have sought the advice you seek. First, you need to run the numbers through Firecalc and get comfortable with your investment strategy. My wife and I have a financial counselor with whom we set very specific investment strategies and he is familiar with our use of Firecalc. The numbers do not lie, and frankly, you simply don't know enough to ever get 100% comfortable. You don't know how long you will live, what health and economic issues you will face (e.g., how will global warming effect your property and income) - you have to be emotionally comfortable with that uncertainty, and I found that takes some time to accomplish.
Also, ER means that you can do other things, it doesn't mean you'll just sit around. Determining what you want to do and getting comfortable with that direction can be difficult. I chose teaching as an important "retirement" activity and have found it personally rewarding, though you will barely cover your expenses. In addition, as I have a law degree (though I was in business most of my career), I am studying to become an arbitrator and mediator. At the same time, I am restoring an old sailboat and doing volunteer work, in part with Score, and exceptional mentoring organization for small business development.
All this being said, after about 16 months, I am just getting a bit comfortable with the lifestyle, and have no regrets leaving the rat race. My health is great, my kids educated and my mortgage is paid and you will be amazed at how little money it takes to live very comfortably when you are not in debt and not raising kids. Good Luck!