As someone who recently retired early, you really need to have a solid game plan on what you want to do with all the time you have. Spend a solid 3-6 months planning and mocking your post retirement days while still working.

The more detailed the plan the better. If you want to go to the gym, what will you do there and for how long and how many days a week?

If you want to have a tech side project, how many hours do you plan on spending on this project? And be reasonable. Don't trade one burnout over another.

If you are planning to learn something new, what are those? and don't just learn one thing. 8 hours plus is a crazy amount of time.

One of those plan should include making new friends post retirement, revolving around activities that are not work related.

It is far too easy to lose track of time without a brand new schedule to fill the void.