Where Stacking Comes From

Habit stacking grew out of the work of Stanford behavior scientist BJ Fogg, who spent years studying why habits stick. His blunt conclusion: motivation is unreliable, so it should not be the only thing your habit depends on. Some days you feel driven, most days you do not, and a habit that needs a good mood is one you will eventually drop.

His fix is the anchor. Tie the new behavior to something you already do without fail, and the routine no longer depends on how you feel. That is why the anchor has to be dependable — "after I pour my morning coffee," if that is part of your normal morning, beats "after my workout," which you will sometimes skip.