When I first retired I felt a bit as you do, PollyJ - feeling guilty if I sat for too long, or didn’t accomplish all my daily targets. I think, in part, it was due to the fact that I stopped working at a slightly younger age than I had planned, for reasons I won’t go into here (and I’d always worked extremely hard). This meant I occasionally got jibes from some family members asking me if I was bored by no longer working full time, and frequently hearing comments from them along the lines of “Oh, I don’t know what I’d do with myself if I stopped working”, “Oh, I’d be bored if I stayed at home all day”, etc, etc.
This used to upset me, and make me feel guilty, but I gave myself a good talking to, realised that they were not in my shoes and also it was something both I and my OH had agreed upon, so basically, it had nothing whatsoever to do with them.
Now, I’m much more settled and happy in myself. The guilt has gone (interestingly, so have the jibes now some of them have had to retire), and I decide each day what I’m going to do.
As you say, you’ve worked your whole life. This time is your time, to do with as you please, and if some days you have done very little, it doesn’t matter. Equally, if you’ve done a lot, it doesn’t matter. What does matter is the feeling of guilt, which you must try hard to push away, as you have absolutely nothing to feel guilty about.
I wish you many years of happy retirement.