Our household recently changed out diet quite dramatically.
We went from eating most meats with red meat or chicken to an all vegan diet.
On day 1, I was about 104kg (post morning poop), though I am 6'5" so looked fine, and I did have a bit of a beer belly developing.
The adjustment wasn't as hard as I expected initially, as there is actually quite a lot of really tasty all vegan foods out there.
We managed to stay 100% vegan for a solid 5 months before I started to find it a bit too restrictive. Sorta having moments of "F**K this, I want steak!!
I was doing it for the health benefits and to see if I could, so decided to adjust it a bit to try and get the best of both worlds.
I am now basically a pescetarian, so eat plants, fish and eggs. I stay away from dairy as it seems that it was the main cause of my beer belly. Now and then if I am at a really nice restaurant I will have a red meat course, but I don't really crave it.
My wife is stricter and hasn't had any red meat since we originally tried vegan.
The current diet is working great for me. I feel happy about the health aspects without feeling restricted. I've dropped almost 10kg and my explosive energy is way up. I'm a martial arts instructor and both my agility and power of strikes has drastically improved from being a bit more nimble.
So the way I maintain my food discipline is finding the diet that works best for me, while still hitting the health benefits I am after and not hating myself if now and then I have something that's not on it.