A long hard walk is good for me to destress. I usually need to do something that involves physical exertion so that means either speed or harder terrain.
Several months ago I needed to clear my head so just set off on a walk and let my wife know she could track where I was with my phone but I didn't know how far I'd walk or how long I'd be. When I got home I think I'd walked a shade under 12 miles, and she said she could see instantly that I was feeling more peaceful.
I've got a few go-to routes in the mountains that I enjoy. The one I do the most is about 7 miles and takes in a beautiful vista near the furthest point. I've walked that route more times than I care to count.
Getting lost in making up new songs on the guitar but I rarely have the time when inspiration strikes and if I force myself to do it I usually end up feeling more frustrated and anxious
A nice long relaxing bath usually does it followed by a scoop or two of ice cream just before going to bed!