It's usually not a willpower problem — it's a design problem.
Most people who try a new diet lose some weight or feel better initially, and a large share regain the weight or drop the habit within a year. This isn't primarily a willpower problem — it's usually a design problem.
Diets built around rigid rules — banned foods, strict windows, mandatory phases — work fine in a controlled, motivated first few weeks. They tend to break down against travel, social occasions, stress, or just ordinary life variability, because the rules weren't designed to bend.
Rigid diets often frame one slip as total failure, which — as with cheat-day culture — tends to produce an abandon-the-whole-thing response rather than a shrug-and-continue one.
Many diets give you a single distant outcome (a target weight, a finish date) with no meaningful signal along the way about whether today specifically helped or hurt. Without a feedback loop, it's hard to learn what's actually working.
No banned foods, no rigid windows, and a daily number that responds to what you actually did — paired with a rolling average that treats one bad day as noise, not failure. It won't guarantee long-term success, but it's designed around the reasons most rigid approaches don't survive contact with real life.