I think what you are experiencing is common to many people in committed relationships. You should have only one chance to make the right decisions and chose a partner with whom you will have children and make a life together. In many cases people disocover they made the wrong choice. I know I did, I simply married too young to really know what it was that I wanted. However, in other cases I think that these feelings of "the grass is greener" lead to misery. You simply have to change your focus. Focus on the good things in your mate. Help him to bring out his good qualities. Place a lower priority and emphasis on the bad qualities. If you don't change your perception you may lose him and you may not like the end result.