Also relevant is how you are treated as an older employee. I see some of my older colleagues patronised by the younger ones. There is no reverence for age, a bit of mild contempt in fact. (They will get old too of course, but that never crosses their mind.) That is not great for mental health, you are past it, should be put out to grass....
But also, some older workers get set in their ways and don't want to do things differently which can cause friction and stagnation. I can see why you wouldn't want to do stuff differently, if you resent having to work, you just want to make life as simple as possible and that includes not changing.
I am middle aged, I try to stay engaged, but it is getting increasingly harder to be arsed. The longer you have been working you see the same ideas come around with a fanfare like they are revolutionary.The first time you welcome them but after the 3rd and 4th time unless you are brand new, you just nod and try and hide a yawn. Yeah, whatevs...
Also, I used to be a hard worker. I am physically fit and not tired, but mentally I have checked out if I am honest. When you get to a certain point and realise there is no point striving, this is as good as it gets, you will never be a captain of industry (!), then it is hard to keep upbeat about working.