I think willpower can definitely be learned! Another word we sometimes use for "willpower" when talking about children is "gratification delay". Take a few minutes to focus on your short-term and long term goals when temptation strikes. For example, when I'm tempted by a tray of dark chocolate, I might say to myself, is it worth the way I'm going to feel at the end of the day when I've gone over my calories? Am I going to let this piece of candy become the gateway to a binge? How about this, self - how about if you can stay on track all day today, you can have a cup of cocoa before bedtime? Etc.
I think with a lot of positive self-talk it's possible! Keep Spark-ing. This is a wonderfully supportive community!