Keepingquiet, I am so sympathetic. I retired after doing an extra year, because I loved my job so much. It was very physical, so I could not really have carried on any further. But my first year was horrendous, I felt I was floundering around trying to fit into something. It has taken 2 full years for me to accept my new normal. I do keep busy, and we bought a little puppy a few months ago. The puppy has been a great addition to our life, and we have a purpose to the day.
But aside from the puppy, we were developing a different routine, for us both, keeping busy most mornings, and putting our feet up in the afternoon. We do gardening, or puzzles, housework, a bit of d.i.y. etc.
The trick is to try not to dwell on the past, and idealise it, just think of the physical drain of going to work every day, had become. You will come to value the peace and quiet, and the time you have to yourselves, especially in the summer.
And then there are the grandchldren, who we can see more regularly, and help occasionally fetching them from school.
Just give yourself time, because eventually it will fall into place, but I know it is hard to believe this in the beginning.