"There's always a conflict between immediate gratification and the long-term goal," explained Opelika psychologist Anne Harzem. "Quite often, we give in to immediate gratification." If the goal is to lose weight, it's difficult not to give into the instant gratification of a slice of chocolate cake. Goals that require several months of dedication to achieve are harder to stick with.
It all boils down to the fact: It's hard to change ourselves, and our habits. We'll all have relapses from our good intentions, but it's important not to lose determination.