this is going to sound generic, but have you tried edible marijuana? can either get you to chill for a while (if dosage is correct) or zone completely out for a couple of hours.

First thing for me: single out my tasks. Do only one thing at a time for a while. Focus my activities to one action only.

(I personally have a bad habit of "juggling" personal activities. Trying to watch a narrative show while playing a game, drawing, or doing chores. It's my anxiety's way of trying to be overly efficient. Might not apply to you.)

While doing this, relaxing music that I can put on long-play, in my personal space with the door closed, and lower (not dark) lighting. Usually an hour like this helps.

Jigsaw puzzles are a good way.
Don't have room to do real ones? There are a number of jigsaw games on steam that are free to play.

Music. Check out Lofigirl on youtube. Pretty chill music, usually what I listen to when writing or just generally in a bad mood.