There are many times - mostly when I am eating something horrible for me- that I wish I had more willpower. There have been time I have had great willpower- for many years I didn't drink pop or eat any desserts or chips. And then, I started eating those things again, and again and again. Once I started, I didn't stop. I wish I could get back to not eating all the junk. There are other things I wish I had more willpower about, too. Like shopping.
The Willpower Instinct: How Self-Control Works, Why It Matters, and What You Can Do To Get More of It by Kelly McGonigal is a book that I read in just a few days, but could use the advice in it for years. There are suggestions in it for controlling your desires - breathing techniques, being one example. And, there is a great deal of scientific information about willpower, meaning I don't feel quite as guilty since there is an actual biological reason that willpower may fail as McGonigal explains dopamine and its release.