What goes wrong when you ignore that existing habits are the best cues?

The most common reason fails: Choosing an anchor habit that is not actually reliable. People often select habits they think they do consistently but that actually vary — like "after lunch" or "when I get home" — which have ambiguous endpoints and inconsistent timing. The anchor must be a behavior you perform the same way, in the same place, at roughly the same time, every single day without exception.

The fix: Identify five habits you already perform every single day without fail — brushing your teeth, making coffee, sitting down at your desk, locking the front door, putting on your seatbelt. For each one, note the precise ending moment: the last physical action that signals the habit is complete. Now choose one new behavior you have been trying to build. Select the existing habit whose ending moment best matches the context the new behavior needs — the right location, the right energy level, the right available time. Write the formula "After I [ending moment of existing habit], I will [new behavior]" and post it where the existing habit occurs. Run it for seven days and record whether the new behavior fires each time.

The underlying principle is straightforward: Attaching a new behavior to an established habit leverages existing automation.