Habit formation relies on the brain and body's state, not just specificity of time.

“I have to break it to you that one thing that you've probably heard over and over about habit formation is not true. And what I'm referring to is this idea that if you're very specific about exactly when you're going to perform a particular habit, that you're more likely to perform that habit. And while that is true in the short term, it is not true in the long term. And the reason for that is that our nervous system tends to generate particular kinds of behavior based not on time, but on our state. Meaning what level of activation is taking place in our brain and body. How much focus we happen to have, how fatigued we are, how energized we are.”