For me? By changing my diet, understanding what "full" actually feels like, and keeping certain things I know I will binge eat out of the house. Plus the knowledge that I can have a bad day or two and get right back on the horse of healthy eating and be totally fine - if I gain a couple pounds I know precisely how to take them off in a repeatable and successful manner. That mental bit is key.
But for food itself - it's eating differently. Basically avoiding carbs and sugars does 90% of the work. It's not a 100% cutting out of my diet like Atkins, but it's prioritizing lean proteins and then simply being fuller for longer.
And part of it is learning you can be hungry for a period of time and not indulge. Which is much easier when you don't have those snacks you can't resist in the house.
It's certainly nothing groundbreaking, but habits are built over time. Motivation fades. I'm certainly not motivated every day or week or even month to eat well - but now it's habit and routine so it's almost more difficult to break it to go to the store to buy junk, or decide to order take out.
Going to the gym on a regular strict basis? I'm not exactly sure what changed. Likely being able to look in the mirror and feel a little vain? And knowing now it's all just about consistency. If I miss a day, just make it up the next day and stay on schedule. No big deal.
All those things stayed roughly the same after I came off Tirzepatide and hit my goal weight. They became harder of course, and I had some rebound (I overshot where I wanted to be on purpose on advice from my doctor) weight gain like most do - but I've now been stable at a healthy weight for over 18mo now. Habits have continued and stuck in place.