It occurs to me that as a Marine, you were accustomed to thinking in terms of the enemy to be defeated. You also mentioned that competition with your peers for promotion was a motivator. In my view, when we make a bad choice it is not a failure of character -- it is a failure of motivation.
If poor health is not a big enough enemy to motivate you, maybe I can share mine. I am an ex-scientist, having spent over 20 years studying and researching infectious diseases. I was not a nutritionist, but I had studied a ton of biochemistry and physiology, so I thought I understood what the CW was telling us about low-fat, high fiber diets. I bought it. And, because I was not an exercise fanatic, I gained weight progressively. Now, having gotten acquainted with Mark's books, Gary Taubes' books and having watched the Big Fat Fiasco videos on YouTube (all definitely recommended), I am mad as hell.
I am mad at the scientific establishment and the Congressional committee led by McGovern (whom I liked, a lot) for setting the whole country on a grain-based diet. I am mad at how dissenting voices were muzzled. I am furious about being duped. I am thoroughly pissed off at myself for not exercising my own intelligence. I am angry that I continued on that lethal path for as long as I did. I'm mad as hell and I'm not going to take it anymore!
You want enemies to fight, I'll give you enemies! Every time you eat your comfort food, you are yielding to big Ag, to the USDA and to the whole medical-nutritional establishment that brought you the deadliest food pyramid they could imagine -- all based on BAD science. Those enemies have put the health of most North Americans in danger. They have shortened the expected lifespan of the younger generation. They have added a crushing load of obesity-associated diseases to the health care system.
Your mission is to use your body as the battlefield, to prove that those enemies do not control you: you will not let them keep those dangerous pounds on your body; you will not let them reduce your quality of life; you will not let them shorten that life. Every time you get up in the morning, eat a high-protein, high-fat, high-veggie breakfast, you're striking back. Every time you take a walk during your lunch hour, you're plotting strategy. Every time you stick to the Primal Fitness approach, you're building tactical strength.
You win this battle and the people around you will take notice. They will ask you how you did it. And you will tell them about the enemies and how to vanquish them!