oaao_
This way of thinking isn't (yet?) /always/ something I'm able to just root myself in, down to the autonomic depths of my lizard-brain or whatever, and I definitely still slip into moments or swathes of variations on, "I am in some way fundamentally wrong/insufficient".
So, sure, it's not a panacea that lets you evade depressive troughs completely, BUT it lets you go through those with a supervisory lens that says, "was that thought/attitude/self-perception unambiguously extra-moral? no? then it's not real; it's just a shame narrative; carry on". That's MORE than enough for a shit-ton of cumulative and lasting progress.
I wanted to address this in a separate comment, especially given the prevalence in this thread of mentioning ADHD and its co-morbidities as further context for struggling with procrastination and 'motivation'.
It's important to be very aware about the ways to win and lose at what feels like the perpetual battle of trying to trick yourself into doing things, and for the crowd who can relate to this, I'd offer some caveats to what you said.
The operative point of "the smallest possible unit of that thing" is never, ever to systematically map out the entirety of a task and then select a small atomic subtask to do; that's just reaffirming your portrayal of something to yourself as insurmountable and monolithic.
Instead, choose the "smallest possible unit" that describes starting a task, and if the descriptions sound absurd then you're doing it right. For example, to a certain disposition, "do your laundry" or "do the dishes" basically invite avoidance, but "put your pair of teal socks into the hamper" or "turn on the faucet / wash one plate" is extremely easy to engage. What usually happens is you autopilot through a bunch of the task (it's OK if it's not all of it), and moreover you end up feeling great about yourself for doing more than you expected, which is strong positive reinforcement.
This is because you're not "shit at doing things"; you just need tricks to start doing things. And if the "smallest starting point descriptor" doesn't carry you through the entire task to completion, that's fine -- you can either parallelize a bunch of things this way and jump between them, and/or, your next "smallest starting point descriptor" is just the next step for that task anyway, so you can jump right back in.
The most success I've had in actively dealing with things like this is when I am able to frame a situation for myself in an extra-moral way and actually believe it - i.e. that something is, like you said, a matter of habit-building and consistency, rather than ontological and exertional good-enough-ness. The tough part here is that many people understand this, cerebrally, but it takes drilling this perspective quite a lot to actually ingrain it into one's belief system.
There's a night and day difference, though, between "well I guess I couldn't do it after all" and "well I guess that's a one-day blip on a four-day streak", and people with 'motivational' difficulties also aren't that great at conceptualizing about & nurturing incremental progress towards an abstract goal, which this also helps immensely with.
All in all I love that your takeaway was, effectively, that 'motivation' can be seen as behavioral inertia that hasn't yet been solved by habit-training. It's not a poetic nitpick at all; at least in my view it's the fundamental operative basis for dealing with the phenomenon of procrastination.