Naturally we are motivated to do what is easiest. That's why when you set out with a lofty goal to completely change your eating habits or start an intense exercise routine after the first few days or weeks, when the initial motivation wears off, we then become motivated by nature to do what is easiest. That's why we need to flip the way we make these changes upside down.
Instead of trying to completely change an entire aspect of your life overnight or, every Monday morning, try to make one tiny change that is so small that you cannot fail. Once you master that tiny chain build upon that in tiny increments. You may not notice the 1% improvement from one day to the next, but after 365 days of 1% improvement you could be a completely different person.
For example: if your goal is to exercise more, think of something so tiny that you could do it every day without a problem - maybe do 10 squats before you settle down after dinner. Those 10 squats may seem insignificant at first, but little by little you could start adding in 10 more squats at different times of the day. After you brush you teeth in the morning, after you go to the bathroom, before you leave for work. Whatever works for you. But if each week you added another session of 10 more squats - you could be doing 40 squats a day at the end of a month. And THAT would add up to some serious improvements in your overall health! But you started with 10. Which takes less than 1 minute. But you started. And your goal was so small that you could not fail; you may have stumbled, but you succeeded with enough positive reinforcement to add on another minute of work - and so on.
It's more likely that you'll be successful if you slowly inch your way to your best than if you start out at 1000% only to prove to yourself that it's not sustainable and end up going back to what's been easiest.
Fogg, B.J. (2020) Tiny Habits: + the small changes that change everything. New York, NY: Mariner Books.
Clear, J. (2021) Atomic habits: Tiny changes, remarkable results: An easy & proven way to build Good Habits & Break Bad Ones. Toronto, Ontario, ON: CELA.