I had a few years where I did nothing except sit in the house, watch mindless tv or scroll the internet for cat videos. I've also been diagnosed with PTSD, so I won't blow smoke up your bum and tell you it gets easier. I'm alone too at 58, but now I try to force myself to go outside. Walks in nature help and I have found the zoo to be a good place to snap out of a funk.
Writing letters may help get some feelings out, but I'm not sure it solves much either. Rants are fun to write, though. One thing that helped me? Thinking about how the people who wronged you would feel if they knew you were unhappy. For some reason, it snapped me out of my funk for a bit. I do not want to give them the satisfaction! Everyday I try to force myself to do something I even sort of want to do, even if it's a struggle. Just going out for a good piece of cake works for me.