Weight Loss help and motivation...?

I can get good at eatting healthy and working out daily for about a week to a week and a half but at that time, I go down the hole. I have a candy bar or something, and I figure oh well I had one, I already did it I might as well have another. I dont know what to do to end this habit. I dont jump in to fast. I stopped drinking pop months ago and only have one rairly. I try to avoid greasy food in general. I think I get tired of the only health"ier" foods I know how to make....salads, subs, and sandwiches. Other than that I dont know what to make for a quick healthy lunch. I vowed this weekend I would get the junk food cravings out of my head and eat what I want and then today I will try it again. Any tips? Anyone else having this problem?