tldr: motivation and discipline are both stimulatory. If you have both, you'll get overstimulated. If you have neither, you'll get understimulated. To maintain the right level of stimulation, decrease motivation to increase discipline and vice versa.
I got inspired by this post and decided to try the recommendations, despite a history of trying to discipline myself and failing. I failed in an interesting way.
What I did: try to increase my discipline by maintaining a low level of discomfort throughout the day. Enough to be constantly aware of it, but not enough to make me ruminate about stopping. This would give me a little more freedom to do things I would otherwise avoid.
The first few days were pretty good, I managed to wake up and go straight for exercise for about 6 days in a row. I visited my grandma (which I usually avoid) and practiced exposure to cold to reduce my energy bill. I was much more in control of myself than usual.
This was a holiday week. Then Monday when my work began, I got up at 7 in the morning after 2 hours of sleep and did the same routine, going out for a run (in the dark) to a calisthenics workout and then an hour of yoga.
Then over the course of the next days I broke down. Today (Thursday) I woke up 5 minutes before my first work meeting so I could pretend-attend it and went back to sleep, while my room is a mess and I'm just eating rice because I can't be bothered to do groceries.
(no worries, this used to happen all the time and I know how to get out of it)
I've taken these observations to define a provisional model of motivation vs discipline.
Before I started the experiment, I was practicing a certain type of renunciation: I would block things that would motivate me. I was in a state of low motivation and low discipline. This felt bad/ineffective.
Then with the experiment I started manually steering myself, bringing me to a state of low motivation and high discipline. This felt good/effective.
My work pulls me in automatically. It's pure motivation. So when I started working on Monday, I was high motivation and high discipline. This triggered the crash, which is bad/ineffective.
Now I dropped the ball on discipline, putting me in a situation where there is high motivation and low discipline. This is my most common situation and it's good/effective.
So my model is as follows: motivation and discipline are both stimulatory. Too high or too low stimulation is bad, there is a sweet spot in the middle (this is an established cogsci fact). Discipline can be seen as "manual" or "artificial" motivation. Renunciation is the opposite of discipline, where you make some motivating things impossible for yourself.
Some people are naturally low on motivation. They benefit from discipline because it brings them closer to the sweet spot. Some people are naturally "just right" on motivation. They benefit from neither discipline nor motivation. Some people are naturally too high on motivation. They benefit from renunciation because it brings them closer to the sweet spot.
And then there's something I'd like to call "motivation replacement therapy", where a medium or high-motivation individual practices both renunciation and discipline, to replace the source of their stimulation from automatic to manual, from S1 to S2.
Going forward, I'll be experimenting with this technique, to see if I can reliably transfer control between S1 and S2 by changing 1) my levels of exposure to motivating things and 2) how much I push myself into discomfort.
Addendum: defining "renunciation"
This does not mean to forcefully keep yourself from doing fun thing X. That would be discipline.
Nearly all of my sources of motivation are on the internet, so what I do instead is to lock up my laptop in a bag with a padlock, and put the key in a time-locked box. This way I don't need to exert any effort to keep myself from fun thing X, it is simply not available to me.
Another way is to go to a meditation retreat, where fun things are sufficiently far away that your (short term oriented) motivation simply doesn't flare up for it.