What is the reason why some men have a mistress?

Hi! I also believe with your opinion. I noticed this with one of my neighbor friend. He don't want to talk about it when I asked him in a polite manner but his action and words clearly leads to that matter. One day, while we are having good conversation in front of our house, our topic is about the result of basketball championship in our place. A sexy lady happened to pass by that made him diverted our topic to the girl. He kept on looking at the girl and uttering some words and kept on staring her until she turned to the next street. He showed so much interest with the girl and he told me his plan of going for morning jog everyday just to show the lady that he still can do the jogging in spite of his age.

For me, I have a mixed feeling and don't know why. I love my wife and always want to give her the best and maybe almost everything that will make her happy. As a normal person, I also admire women with beautiful features like pretty face, sexy body, white and smooth skin and more. If that kind of lady seductively approach me in person, I'm not sure if I can still control myself. What more if we belong to one group or seeing each other more often because of work, the feeling may grow deeper. It may lead to special relationship. As a married man, I won't start the first move.