The chain matters more than the volume
A habit is a thing you do without deciding. That automaticity is built by repetition, and repetition requires *not stopping*. So a small thing done daily beats a large thing done erratically — not because the small thing is more valuable, but because it's the only one that survives to become automatic.
Which means the daily minimum must be low enough to clear on your worst day. Ill, hungover, three deadlines, four hours' sleep. If it can't survive that, the chain will break, and once broken it usually doesn't restart.
Set a floor, not a target
- "Review my due cards" — even if that's eight cards and four minutes. The scheduler decides, and on a bad day it's a small ask.
- "One 25-minute session" — that's it. That's the whole obligation. Start a timer and stop when it rings, guilt-free.
- "Open the document and write one sentence."
On most days you'll do more, because starting is the barrier and once started you continue. But on the bad days you do the floor, the chain holds, and the habit survives to the next good day. That is the entire mechanism.
Attach it to something that already happens
Habits run on context. "After I make coffee, I do my cards." The existing behaviour is the cue, and you're borrowing its reliability rather than trying to manufacture new reliability out of intention. Intention is what you have on Sunday; context is what you have on Wednesday.