take this with a grain of salt because for the most part im told i have remarkably relaxed muscles, but sometimes i do get some muscle tension especially when stressed or overstimulated, mostly in my back. ive found what helps me the most in those times is a combination of being really warm and stretching. a nice long hot shower or bath, being bundled up in a warm blanket, or even just turning up the heat a lot in my apartment helps a lot.

if thats not enough ill do this thing where i like stretch the muscle and flex it at the same time, i guess youd call that resistance stretching, then letting the muscle fully relax. doing that a few times helps a lot but can be hard depending on which muscle youre getting tension in.

theres also some breathing exercises you can do to relax yourself mentally as well as physically. one of the easiest is you take a big deep full breath through your nose (doesnt matter how fast just a full breath), then blow it out slowly through your mouth, pursing your lips like youre blowing out a candle, over 10-20 seconds or longer if thats comfortable for you. you just do that as many times as you want. i was really skeptical of this one because it sounds so simple but it does really work. it kinda gives me this mild anti-tingly feeling all over and i can feel myself relaxing as i breathe out. you can do that while lying in bed or the bath and try to consciously relax your body as much as you can while you do it.

hope this helps!