I've been frugal all my life and "struggled" to spend more in retirement, too. It's not just frugality, though, it's really a philosophy of life, simplicity. Keeping things small, simple, and uncluttered, so I can focus on what I really enjoy and care about.
I'm different, in that I don't seem to want or care about most of what normal people do -- you know, kids, family, nice houses, travel, busy social calendar, nice cars, lots of stuff, plenty of entertainment. I get my joy from simple things like reading, taking walks, going to the park and walking my dog, fiddling on the internet, hanging out in the backyard, playing a game, reflecting, or just relaxing. None of these things cost any money.
So despite my desires to spend more, I'm only moderately successful. I can't really change who I am at this point, nor do I want to. Buying stuff just doesn't bring me much happiness, generally speaking.
Now, there have been a few exceptions. I "bought" a dog. I bought a bike. I spend pretty freely on good food. I bought some better patio furniture. I bought a shitload of books. I buy gourmet food for my backyard squirrels and birds, lol. All of those things made me happier or more content. If there's something I want, and I think it'll genuinely bring me long-term happiness/contentment, I'll buy it. I don't deprive myself. But I've only been moderately successful in increasing my spending so far, even though I know I should. I yam who I yam.