One of the most frustrating things about changing your habits is realizing that motivation doesn't stay.
You can feel completely committed on Monday and struggle to care on Thursday. That doesn't mean you've failed. It means you're human.
Motivation is useful for getting started, but it is a poor foundation for a long-term lifestyle. If your plan requires you to feel motivated every time you make the right choice, eventually the plan will break.
The answer is to build systems that make good decisions easier. Prepare food before you're hungry. Keep useful foods available. Put your walking shoes where you can see them. Schedule training instead of waiting for the perfect mood.
More importantly, stop turning individual mistakes into an identity. One large meal doesn't erase your progress. Missing a workout doesn't make you lazy. Having a difficult week doesn't mean you're back at the beginning.
The mindset that lasts is not 'I will never mess up again.' It is 'When I get off track, I know how to come back.'
Real change is built by people who can recover. They don't need perfect days. They need enough good decisions, repeated often enough, to create a different life.