AFAIK I don’t have autism or ADHD, certainly I’ve never been diagnosed with either, but routines are a good thing. If you have a functional routine that you follow, you probably won’t make many mistakes and you’ll have less cause to question whether you missed a step or did something correctly. To put it another way, if you know the rules going in, you’ll probably do it right.

I’m consistent enough that any space I regularly occupy (my bed, car, office chair, etc.) has wear patterns reflecting the way I use the space (mark on the wall where my hand goes when I sleep, dent on the car door where my elbow rests, etc.). My wife teases me, too, for having patterns … But I rarely fumble on any task I’ve performed more than two or three times and I don’t have to work hard to do things familiar to me. A few times I’ve been ill but doubted it until I bungled a routine.

As a final point, I would direct you to a scene from the excellent Meet Joe Black, but lamentably I cannot remember enough about it to find it online. In this scene, the protagonist references that shaving is a simple and consistent enough process that you can perform other mental tasks while physically occupied. If you have good routines, the same thought process applies to all recurring and regular tasks. (In case you have not seen the movie, I assure you that both the scene and movie are significantly better than I’m making them sound.)