A king has opportunity to sin like no other person. An ancient, sovereign king could sin and none could question him.
Christians, who are kings and priests to God, must take great care with this sin and every sin that erodes self-control. We need to see the danger of it in the right way. The sinner thinks he is in control of the situation, choosing to follow his own his own desires, and able to leave off any time he wishes. The more accurate picture of what is going on is that he is being drawn irresistibly by sin. His strength is being drawn out of him, and he is being reduced to a helpless weakling, unable to fend off spiritual bandits lying in wait for him.