My plan for retirement was to do the things I didn't have time for when I was working. I find, though, that I waste more time than I used to, and I end the day not having done the things I wanted to. I thought I'd do more writing, recording, reading, and puttering, gardening, woodworking, music lessons. I don't do those things, or go riding either bikes or motorbikes. I was/am avid about both. My honey stays up late and sleeps in. I have mornings alone 7-8, then my bath before our son gets up, but try to stay quiet. Son gets up around 9, and we walk the dogs most mornings, weather permitting. Then at 10 he's in the tub and I watch/exercise his dog (she's very high energy!). By the time he leaves for work half the day is already gone! Afternoons are typically honey-do time. I'm just not organized enough.
Days on the road, at the condo (time share), or on vacation are actually more productive! I write music, do research, get out and about. And I learn so much.
Ran into an acquaintance at a grocery store a few weeks & had a short discussion on retirement. We came away with the short summation “it’s fun & productive, it can be productive fun”. Just not always both at the same time. I find, with most of the day to myself, I let my mood dictate the path. I mostly like & trust my moods. They certainly guide my music. Just hafta know how to walk happily away from some of them.
I laughed at your ‘half the day gone’ comment. My wife & kids would tell you one of my standard weekend comments, usually around 10 AM, was ‘half the day is already wasted’ as I waited impatiently for them to get up & around.