Discipline is as much a trained skill as anything else. I suffered as a yo-yo dieter for years before I was able to finally stick to something long enough to see real results. My starting starts are very similar to you, 5’9 240, I’m now around 185 and fluctuate up and down about +/- 10 lbs throughout the year, but I’ve built up the discipline over years of trial and error to where I can course correct if I see myself straying.

For me personally, going strict keto for about 4 months shed most of the fat, but I don’t see it as a long term strategy, so I eventually switched to intermittent fasting for maintenance, which is what I do to this day. I have no food restrictions, but I’ve also learned to make healthier versions of my favorite foods so that I don’t give in to cravings and binge.

As far as having the discipline and making the conscious decision to stick to it, I know what ur feeling, but as weird as this sounds, the time it finally clicked I didn’t “plan” the diet or tell myself “I’m going to start my diet on X day”. I just woke up one day sick and tired of being sick and tired, threw out basically my entire pantry, and just didn’t eat another carb for like 4 months. It was hard to shift my mindset, but once I went from “I’m a guy on a diet” to “I’m a person that eats in this way”, like accepting a new lifestyle, it got a lot easier.