Psychological studies link intrinsic motivation to long-term goal adherence

Psychological research suggests that while temporal milestones like the start of a new year can encourage people to set new goals, long-term adherence depends heavily on intrinsic motivation. A 2025 study published in Psychological Science, which tracked adults in the United States and China, found that motivation derived from the experience of the activity itself was a stronger predictor of continuity than future-oriented results like health improvements or financial savings.

Regarding the timeline for habit formation, a 2024 meta-analysis of 20 studies involving 2,601 participants found that the popular belief of a 21-day rule is not supported by evidence. Instead, the study found that the median time required to form a health-related habit ranged between 59 and 66 days, with averages between 106 and 154 days. Individual variation remains significant, with reported durations ranging from 4 to 335 days.