It's not easy to retire for most people. While we look forward to the time off of work and getting a second chance at life, we also have to remember that people are creatures of habit. Since you've spent the last four or five decades working your hands to the bone, you probably don't know any other way. It can be disconcerting at first to go from having a daily routine, a job, and a “life” to suddenly having all the free time in the world to do whatever you want.
At first, it's easy enough. The first few weeks seem like a vacation and that makes it less complicated for some people. It tends to be that people get settled into their routines and start to just go through the motions. For the first little bit, taking it easy and having a good time can be great. Eventually, though, you might find yourself struggling to actually enjoy things or have some type of structure to your life. The people who work toward creating a retirement environment that they love will actually fare much better than those who just stop working. The difference can be seen in mental health, emotional health, physical health, and overall happiness.
You don't have to structure every minute of every day. You don't have to have a full 10 or 20 year plan for what you're going to do. I, personally, started small. I started volunteering at recreation centers and my background in sports was helpful for that. I decided that I was just going to go do this sometimes as a way to get out of the house, have a good time, and interact with others. It was a simple step, but it was a step.
Make it a point to do the things you want to do. Take the time to find new hobbies and plan things that you've never been able to do before. If you are lonely, go make friends. If you prefer to do home-like activities, consider visiting the library, the local bookstore, or spending some time reading at the coffee shop instead of sitting at home. Even just being around people, for a few hours a day, can change your attitude completely.
Retirement isn't as easy as it looks, but it doesn’t have to be a challenge. It's just something that you have to be prepared for. That way, you can actually enjoy your retirement and not just get through it.