Definition
Friction is the sum of small obstacles between a person and a behavior: the steps required to start, the decisions that must be made, the physical effort involved, the ambiguity about what to do first. Friction is invisible until measured, but it is the variable that explains why two people with the same motivation produce very different behaviors.
In habit design, friction is the primary lever. To install a behavior, reduce its friction toward zero; to remove a behavior, increase its friction until competing options win. Motivation is a slow knob; friction is a fast one.
Why it matters
How it works
Friction shows up at three layers: physical (the laptop is in the next room, the gym is across town), cognitive (which version of the habit do I do today?), and emotional (it feels awkward, exposed, unfamiliar). Each layer adds startup cost. When the cost crosses an invisible threshold, the brain quietly substitutes a lower-cost behavior — and the substitution feels like not feeling like it, not like a design failure.
The practical method is to walk the steps from current state to desired behavior and count them. Then reduce the count: lay the gear out, pre-load the file, pick the single smallest version, eliminate the choice. For a habit to be broken, do the reverse — add steps, hide the cue, make the unwanted behavior require a small but real act of will. The behavior that wins is almost always the one with the lower total friction.