[irremediable]

People have written books about habit formation, e.g. Tiny Habits. The principles are fairly convincing.

Choose one of [walking more, eating healthy, strength training, sleeping early, etc].

Anchor: use an existing habit as the trigger for your new habit. For example, if you tend to eat lunch at the same time every day, and have free time after it, your anchor could be "as soon as I finish lunch". Maybe set a phone reminder if you're not good at remembering.

Behaviour: do a tiny, accessible version of the desired behaviour. e.g. if you want to walk more, this might be "I'll leave my house". You're going to ramp this up over time, so starting small is fine.

Celebration: do something simple to provide positive feedback for engaging in the habit. Even just something like "I will smile and let myself feel good for five seconds".

Do that for a few days, scale up the behaviour slowly, and eventually you'll have built the habit. Then add on a new habit.