How do you successfully maintain a calorie deficit over the long run?

I’m currently a lump of chocolate and cheese, but once the new year hits, I’m determined to make 2026 the year I finally get back to a healthy weight (I’ve lost about 20 pounds, with about 80-100 to go). I’m pretty good about exercising regularly, but, as they say, abs are made in the kitchen. Those who have successfully lost weight, is there anything you particularly recommend for maintaining a calorie deficit to lose the weight, and then avoiding gaining it back later on?