If there is such a thing as “one habit that rules them all” it might be the habit of overriding the voice in my head that says, in the moment, that I don’t want to do something when, in theory, I actually do want to do it.
For those who are really interested in getting to the bottom of habits and behavior change, why not face this conflict head on and turn the act of overriding this voice, itself, into a habit?
Start by committing to do one thing, every day, that:
A) You don’t want to do, and
B) You don’t already do automatically.
It should be something that takes under a minute (it’s really a split second of self-defiance that is the brunt of the work). The specific action that you do can repeat from day to day, as long as you continue not wanting to do it every day, and it continues to be non-automatic.
It’s the anti-habit, in a way. As soon as the action becomes automatic, or enjoyable, stop (or don’t, but don’t continue for the sake of this habit). The point of the “I don’t want to” habit is to put continuous, deliberate, willful pressure on that voice that says “I don’t want to” when, actually, you do.
Changing all kinds of other habits will then become much easier.