>weight training
I should, but I can tell you for certain that I won't. What's the difference between aging to death and being bored to death? Zip, except I'll have more time to do what I want with the aging-to-death route. That said, as I approach 67, I can literally feel the loss of strength. Enough so that I may yet put up with being bored.
Or maybe just take a pill, hhh. How about testosterone? Sure way to have me kill someone or have the TSA kill me (remember, Louise won't let me stand with her in TSA lines, says I make them edgy.)
>psychologically difficult
Yes, very difficult. At goal, one of your first thoughts is "Now I can have cheesecake." No, you can't. You have to stay pretty close to what you were doing, maybe branching out slowly with the aim of a better-balanced diet. That's the really hard part because many staples of the recommended diets may not work for you personally. I can't eat fruit. I can eat chocolate eclairs and they won't impact me as negatively weight-wise as a bowl of fruit.