Being able to defer gratification means waiting to get what you want. It is highly correlated with life-success, such as academic and professional performance.
Longitudinal studies that have been replicated around the world do present powerful evidence that controlling one's impulses has wonderful benefits.
However, we should also note that there are many psychological barriers that need to be overcome in order to improve one's willpower. This is not a trivial task.
Predicting Adolescent Cognitive and Self-Regulatory Competencies From Preschool Delay of Gratification: Identifying Diagnostic Conditions for the original paper.
Oh, The Temptation at Vimeo for another video of kids being tempted by marshmallows.
Deferred gratification and Stanford marshmallow experiment at Wikipedia
- An updated marshmallow experiment suggests that many of these behaviors are due to environmental factors.