My body doesn't feel the passage of time consistently. So my mind is never prepared to switch activities when it needs to.
And there are times my brain stops working on a particular task and nothing can get it started again. It's like a leg going out, you just can't stand on it.
This isn't occasionally where habit could be picked back up. This has been a problem every day of my life.
In my experience, this has been the death of every bit advice I've gotten from a neurotypical person. A lot of them keep circling back to discipline or trying harder as a solution to a problem they can't make sense of. Lack of understanding isn't their fault, this is so far outside their frame of reference they can't make sense of it in a single conversation. Fortunately understanding isn't required, only the acceptance that other people have limits they don't have themselves.