“Habit is thus the enormous fly-wheel of society, its most precious conservative agent.”William James · The Principles of Psychology · 1890
Habits become well‑trod paths in the mind, and repetition makes them easier to follow without conscious effort.
James said every repeated action leaves a deeper trace in the brain, just as repeated footsteps leave a visible path through a meadow. At first you must concentrate to tie a shoelace or learn a new letter. After enough repetition, the body does it almost by itself, with no conscious effort.
Why it matters His idea about habits underlies many modern methods for learning skills and breaking bad ones.