When making a decision, we often overestimate our ability to resist temptations or urges. This belief allows us to make decisions that will increase our exposure to these temptations and, thus, increases the probability that we will succumb to them. This is the result of the empathy gap effect (our inability to empathise with our future selves) especially when we will be in a different mental state in the future. For example, it’s easy to think that we won’t eat a snack when we’re full but we might find it hard to fight the temptation when we’re hungry.
A study was conducted on students in a cafeteria where they were asked to rate and choose a snack that they would have to keep for a week to win a small prize. Some students made their choice before eating and often chose their least favourite bar, others chose after having eaten and often took their favourites because the perception of their restraint ability changed by being full. The students that chose their least favourite snacks were more likely to avoid eating it during the week.