Hal - sitting on your duff, constantly tying flies, is NOT good therapy during retirement.... You will soon think it is a chore, and treat it as such. You MUST do a variety of things... tie some flies (for ENJOYMENT, not as work), fish (and, in my case, hunt, too), take care of your grandkids, go camping, take some vacations (that don't interfere with your sports), etc. I usually write a magazine article on a monthly basis, just to keep my hand in - but now it is on something I enjoy, not something for an obscure scientific journal. Takes me about a day's total time, with a little extra time for doing research/testing and pictures. But if I had to do it every day, I soon would be bored. And I can skip a month when I don't feel like writing. Another thing about it is I have to be well-read to keep up to date, so I do a lot of reading.
Be careful! My spouse has a part-time job. If she didn't, we would probably be divorced or kill each other by now. Yeah, we take vacations together, do many things together, and have a much better relationship now that we aren't in each other's hair constantly. That can be a MAJOR problem.
Retirement is a time for FUN. But everyone adapts to it differently. If you get into a rut, you get bored, feel useless, feel sorry for yourself, and before you know it, life is OVER. So enjoy it, but don't key in on one thing.