A 2009 study at University College London followed 96 people who each tried to build ONE simple new habit — drinking a glass of water in the morning, doing 50 sit-ups before dinner, taking a fifteen-minute walk after lunch. Every day, the participants recorded how automatic the new behaviour felt. On average, it took 66 days — not the popular '21 days' figure — for the action to feel truly automatic. But the range between individuals was huge: some got used to their new habit in as little as 18 days; for others it took 254. The lead researcher, Dr Phillippa Lally, said that missing the occasional day made no meaningful difference. What did matter was starting simple and repeating the action in the same context.
