There are a variety of other factors:

  • It isn’t worth it; the cost is more than the benefits.
  • He might never have the opportunity, possibly because he doesn’t go out of his way to make such a thing happen.
  • A personal code of honour (morals/ethics), and strong-mindedness to carry it out.

If you mean what permanently stops a man from cheating after he has started cheating, the answers could involve:

  • A personal change occurs in the man.
  • The cost is no longer worth the benefit, the man is logical enough to realize this, and the man is strong-minded enough to carry it out.
  • The man gets bored of cheating. (Specific case of cost/benefit case).
  • The man and his woman make up, if there were arguments that lead to the initial cheating.
  • Death, or severe injury to the man.