There's a relationship between having regular habits and mental health

At the extremes, yes. If your habits are very very regular and you are very very attached to them, you might have OCD :-P

the chief benefit is that forcing yourself to go through with things that aren't fun but which are necessary for living above the level of an animal acts like acid to the narcissistic patterns of thought

That line of thought is well expressed in early Protestantism -- see e.g. the Puritans.