May I ask what AD you are using? I am also dealing with dark days however in my case its situational, not internal.
I'm not familiar with REST, however I had years of DBT. Anger, for example, is a hard emotion to deal with. I'm too exhausted to do my chores after an 8 hour shift. I do some but not all. I know I have purpose, however I'm in a situation that's really bringing me down.