Teeth drift back toward where they were if you stop wearing the retainer. Old habits do the same thing.

Change holds only for as long as something keeps holding it. Anything moved out of its original shape tends to drift back, and that pull does not expire just because the change is complete, which is why the maintenance phase is where most progress quietly disappears. Arriving and staying are two separate jobs.

Pick a change you have already made and work out what is currently keeping it in place. Put the maintenance version into your week at a size you will genuinely keep: one session, one check, one evening. Treat drifting back as the default rather than a failure of character.