Self-control is doing something else to prevent doing something you should not due. For example, if you are trying to sober up and not drink alcohol you will deny drinking. If someone is on a diet they will not constantly eat pizza and drink soda, they will take everything from their willpower to stop this negative habit to help them live a longer and healthier life.
Self-control is known as self-reinforcement and self-punishment. You could easily say okay I will eat this slice of pizza if I work out an extra thirty minutes. You can easily make it work you just need to want it as bad. It is known that self-control is a temporal issue, making you choose between alternatives that soon enough have consequences. In a way, how much is self-control, and how much is self-punishment? I remember when I was on my "diet" in high school and when I did not see any difference I would "self-control" by not eating and over-exercising. At that point, it was self-punishment I just was not educated enough to see it till recently when I started to recover.
Attached is a video that explains what self-control is: