“80% full” is not a specific number, but rather an idea: Eating until “just satisfied” or “no longer hungry” but not full or stuffed.
This habit will continue to teach you appetite awareness as well as build and intuitive understanding and control of hunger/fullness.
This is another foundational habit, like eating slowly, which means you can always come back to this habit no matter where you are, what you are eating or whom you are with!

You will learn to sense your hunger and satiety cues properly, as well as distinguish physical hunger from cravings.
You gain clarity and be able to identify situations/cues that contribute to your eating habits.
Improves mindfulness.

Understand that this habit, although simple to understand, is quite difficult to actually do. It will take some trial and error and lots of practice.
Pay attention to the following hunger/satiety cues:
- Hunger cues: “hunger headache”; lightheadedness or “spaced out”; being “hangry” (hungry + angry); growling or empty-feeling stomach; etc.
- Over-fullness cues (ate too much): feeling stuffed/bloated; heartburn; feeling nauseated or gassy; feeling heavy and sluggish; etc.
- Satiety cues (ate just enough): feeling energized and no longer hungry; feeling generally satisfied; feeling as though they could get up from the table and do something (such as go for a walk); etc.
If you have to get to 100% full to understand what 80% is, that is okay! When you get to 100% full, really listen to how you feel physically and emotionally. Then for your next meal, dial it down a little and try and stop just before you reach this point.
Practice, practice, practice! The goal is to be at least 90% consistent with this habit before you move on to the next one.