If something has been missing from your life previously - then maybe it's possible to "get it in now"?
In my own case I'm very aware I didn't go to University (armed forces family, the intelligent one of my parents was the one that was away a lot - ie my father). So I thought I'd make it up when I got to retirement age - by doing an Open University degree. But, by the time I got to retirement, it wasn't just the 5% that are "university material" that were going to University - another 45% were as well. So I thought "What's the point of doing a degree - now that lots of other people besides the original University people are doing so? It would prove precisely nothing and OU degrees used to be reasonably priced - but they've put the price up a lot".
It took literally years to renovate the house I moved to West Wales for - as it all takes longer than my own area. But it's finally finally done and the house is finished - so now I've finally "got a retirement" so to say. So I shall be watching this education gap - and basically at the moment I'm doing more "informal" studying of whatever takes my fancy - and "filling in the gaps" in my knowledge of how Society functions etc. Guess that's one thing the Internet comes in handy for.
From other peoples point of view - I'm guessing there's quite a few people who have "gaps" in creative activities. I see a lot of that going on around me and admits to feeling envious of those who do have creative interests and are good at it - so there's all sorts of "arty" type things that I see people of all ages doing around here. So, if you've got those sort of interests and talents = never too late to do that for instance. Where I am now - there's various singing groups too, for instance, that people who can sing (and some that can't) join and I'm wondering about that (though I'm in the "can't sing" category).
That's my theory on older age anyway - figure out what is "you" - but was missing in your younger life (ie because you didn't have the time or didn't have the money) and see if you can do it now.
So - for myself - besides generally informally studying my Society around me - gardening is another thing I didn't get a chance at when younger (couldnt afford a house to start with and then couldnt afford for it to be one with a garden) and so I'm doing all sorts of experimenting with teaching myself to garden. So people walk round my garden - now I've got one - and out come the questions - as they know I experiment with what plants I get to some extent/try to grow a bit of food for myself/am starting to add in some medicinal plants. So they don't recognise a fair bit of what I have here - because it's one of my "experiments" - so they get told about that and given a bit of surplus fruit (if there is any).
The gardening (foodgrowing) ties in with having been brought up with a diet that was restrictive even by 1950s standards - and so I've had to teach myself about even pretty "common or garden" foods when I grew up and still teaching myself all the stuff about food that I missed out on when growing up (yep...as you can guess....if it's something unusual one can grow in a British garden = I want it and have possibly added some to my garden). The rest of the "food experimenting" involves a lot of Amazon purchases - as this is a small remote town I live in now (frustrating - now I've got the money to eat what I choose finally) - but I do what I can and the choice of available foods here has grown somewhat since I moved here thankfully...so I'm in there buying/trying it and visibly "hoping for more (choice)".
So - yep.....overall message, I would say, for retirement is to ask oneself "What was missing from my younger life that is "me"?" and then try and fill that gap/learn that knowledge/etc by getting it in now. Guess it's a case of "Better late than never" and at least you won't have spent your whole life missing out on those things that are "you" - but you couldnt get them when younger (for whatever reason).