Dr. Walter Mischel, now a Columbia University professor of psychology, studied self-control in young children in the 1960s. The experiments involved putting a child in a room with a tray of marshmallows. The studies were designed to see whether the child could resist eating marshmallows for a certain period of time, thereby delaying gratification by exercising self-control.
Some children could delay more than others, as you might guess. Mischel and his colleagues then tracked these same young children into their teens and then into adulthood. They found that their success in life had a lot to do with self-control.
So, what determines self-control? Based on hundreds of hours of observation, Dr. Mischel concluded that self-control depends on what he calls "strategic allocation of attention". What he means by this is how well a person can avoid thinking about what is tempting them. Once you realize that willpower is just a matter of learning how to control your attention and thoughts, you can really begin to increase it. Mischel noted that using mental tricks is not enough. You need to turn those tricks into long-term habits.
Can you apply this conception of self-control to your own experiences with delay of gratification? If you find that it applies, why not use it to be more in control of what tempts you.
You can read more about all of this in the article, "Don' t! The secret of self-control" in the May 18th (2009) issue of The New Yorker magazine.