“Self-control is the ability to regulate one’s emotions, thoughts, and behaviour in the face of temptations and impulses.”
Individuals with low self-control tend to be impulsive, insensitive towards others, risk takers and short-sighted. The success we achieve in our relationships and careers is directly related with our self-control.
There’s an interesting experiment done by Walter Mischel on children which supports the relationship between self-control and individual’s success.

The Mischel Experiment [1]

In the 1960s, Walter Mischel tested four-year-old children for self-control in “The Marshmallow Test”:
The children were each given a marshmallow and told that they can eat it anytime they want. But if they waited 15 minutes, they would receive another marshmallow.
Follow up studies showed that the results were well verified with these children’s success levels in later life. It was found that children who showed less self-control by taking the single marshmallow, were more likely to develop problems in their life later.

A strategy used in the marshmallow test was the focus on “hot” and “cool” features of an object. The children were guided to think about the marshmallow’s “cool features” such as its shape and texture, possibly comparing it to a cotton ball or a cloud. The “hot features” of the marshmallow would be its sweet, sticky taste. These hot features made it more difficult to delay gratification. By focusing on the cool features, the mind diverts from the appealing aspects of the marshmallow, and self-control is more achievable.

Inference

So, conclusively we can say that the best way to delay gratification is by diverting our thoughts. Instead of giving into instant gratification, if we focus on long term harmful effects of such activities, we could empower our self-control and retort temptations.

Reference:
[1] Stanford Marshmallow_Experiment – Wikipedia