Here are two quotes from Robert E. Lee, the Confederate General, that teach the importance of self-control:
The first is an observation Lee made about how he hade made military command appointments. He said, "I cannot consent to place in the control of others one who cannot control himself."
The second is Lee's response to a mother who asked the General to give her infant son a blessing. Lee said to her, "Teach him to deny himself."
These are great quotes. People who cannot control themselves are disqualified for leadership. And the way we learn self-control is by learning to deny ourselves.