One Step Forward... Two Steps Back

So, today was a day of mixed results with my attempts at getting healthier. My calories during the day were awesome. They were a smidgen high, but that's because I ate some nuts and, as I'm sure you know, nuts are high in calories and fat... but the good kind. I went to Curves after work and had a good workout. It wasn't great, but it was good... As I was leaving, one of the members announced that her son was selling candy bars for band. I was a total band geek in school and I had to sell those same candy bars. So, I gave in and bought one of each... there were four kinds. I held strong when I got home and started making my dinner... a healthy chicken stir fry... but those candy bars in my purse were calling my name. I ate a sugar free popsicle in hopes of curing my sweet craving, but those damn candy bars kept saying, "Come eat me... you know you want to." So, I gave in and ate one. It was good, but not amazing. Then I ate my dinner which was amazing, but I kept thinking about the other candy bars. So I ate another one. I'm ashamed that I have no willpower, but I'm trying to change that. I'm working on it and I know it's going to take hard work and motivation.

What do you do when something you know you shouldn't eat is calling your name??? How do you keep strong? Is it possible to magnify your willpower??? Thoughts?