Some people might think this is not a virtue, and they could be right. However, to become a young retiree you have to have it. One of them said that when he was a kid, instead of going to the playground or talking between classes, he prefered to advance his homework.
Delaying enjoyment is something that can be learnt by children. It will give them more freedom because those individuals who find it difficult to delay gratification will often find it intolerable to have to put off their enjoyment.
Deferred gratification is also related to impulse control. In fact, there is a link between addictive personality and the inability to delay gratification.
Besides, it can be used to increase motivation. For instance, people on a diet can have a day off to eat junk food if they have been compromised the days before.
Last, psychologists say it's better to seize the day, which probably is right, but, again, to retire young you have to have the capacity of "seizing the day" by thinking of the future.