I generally advocate for the complete opposite, as a person with AuDHD and a lot of executive dysfunction:
If an activity has value, then it is worth half-assing.
If you can go whole hog on it and do it with full effort, great! -- But you are often better off doing it kinda half-assed, knowing full well you didn't put your all into it, then you'd be if you just didn't do it because you can't do it "properly" and felt bad about it.
Be it work, schoolwork, cooking and eating, cleaning, self-care things. Whatever.
If it is an activity that has any value, it will still have more value when half-assed then it would have if you felt guilty for your inability to do it whole-ass and then just didn't do it.