How do I get myself to use willpower to make better food choices?
You actually need to stop relying on willpower to lose weight. Willpower is limited, so you can't rely on it for every food choice. Instead, use your willpower to make unhealthy food inconvenient and eating healthy very easy to do. Your sub-conscious part of your brain will always try to make the most efficient (lazy) choice. You can take advantage of your inherent laziness by making eating healthy the easiest, most convenient choice.