Men are unfaithful because they choose to become one. That's the only explanation valid. You can blame your wife or your environment, but in the end, it's you who decide your fate...not your wife. Wife tends to become unfaithful also for the same reason...they chose to become one.

So, best thing to do is to set your mind that once you committed yourself to that person, that's for good. You did not marry/choose a perfect person. In your relationship, there will always be trials, but it's how you both deal with the trials and chose to be what you want to be.