It sounds like your body and mind need a rest. IDK about you, but even though I'm healthy and in pretty good shape for my age, my legs, glutes, lower back, shoulders, etc. get really tight from sitting all day and into the night (I work similar amounts and have for years).

I have a couple of techniques that work for me.

- Taking breaks. Sometimes it's reading HN, other times it's preparing a small meal, or just walking around, or whatever.

- Mental time off. When I have something stressful with a client or there is some big meeting set for a few days from now I prepare and that's it. When I'm comfortable or even if I'm anxious I just tell myself, "I'm not thinking about this again until such and such day or time." It's really empowering and works. Probably the best thing I do.

- Yoga, just a little to loosen up, I like Tara Stile's videos on YouTube, they are for all ability levels.

- Mobility work. One good example is the Limber 11. Learn about your body. A foam roller, a ball, and some light aerobic work get your blood flowing and endorphins going. It just feels good. Also a little time at the gym you get to see other humans and it can be mentally relaxing since your body is doing the work instead of your brain.

- Skydiving. It's a sport that I really enjoy. I know it sounds odd but as soon as you step on a plane the rest of the world just goes on hold. You're focused on that jump and what the objective is (4-way, competition, whatever) that nothing else really matters. It's a common theme with skydivers. Perhaps you can find something similar in your life.

- Learning. I enjoy learning about new things and it's a mental break.

Just take it easy, do what you do well, learn how to turn focus on and off. It a skill that you just have to work on like anything else.