The idea was popularized by Charles Duhigg's The Power of Habit, building on research at MIT: every habit runs on a loop of cue, routine, and reward. The cue is the trigger — a time, a place, an emotion, a preceding action, or the people around you. The routine is the behavior you perform. The reward is the payoff that satisfies a craving and teaches your brain to encode the sequence.
The more the loop repeats, the more the brain hands control to the basal ganglia, so the routine fires almost automatically once the cue appears. That's why you can drive a familiar route without thinking or brush your teeth without deciding to — the loop has been carved deep.
Understanding the loop is practical. To build a good habit, make the cue obvious and the reward immediate and satisfying. To break a bad one, keep the same cue and reward but swap the routine — the golden rule of habit change. A missing or vague cue is the most common reason a new habit never sticks.
Daychain is built around the reward half of the loop. Each day you complete a task, a chain link is forged with a satisfying animation and a haptic tap, and your growing streak becomes a visible reward you don't want to break. By anchoring tasks to reminders (the cue) and celebrating each completed link (the reward), the app helps the loop close on its own until the routine runs without willpower.