Sometimes we just make the wrong choices.
Two and a half years ago I weighed forty pounds heavier. There was no magic formula, no secret ingredient, and no mysterious pills from African cacti. It involved learning to discern between what my body really needed and wanted from what I am feeling at the moment. In other words, hunger can lie. What feels like hunger might really be thirst or exhaustion or dissatisfaction. I learned I could loose weight by paying attention to those little details and saying "no" to eating for the wrong reasons.
In our spiritual life things are often the same. We confuse the emotions and movements of our hearts as leading us to material comforts when they are really leading us to prayer. We're exhausted or lonely or frustrated and we turn sin in various forms: pride, greed, envy, lust, wrath, gluttony, or sloth. As you observe your Lenten penance and you struggle without pop, snacks or other things take a few moments pray and ask Christ to fulfill your needs.
That is always a good choice.