Across the fence they see pasture, that is, greener grass. They see a friend or co-worker of the opposite sex who listens to them. They see this person in all their good moments. They don't see their bad attitudes. They don't have to live with their bad choices. They don't see them when they are unattractive. They only see them in the sunshine.
If it is not another person that people see, perhaps it is the peacefulness of the field. No more fighting. No more rejection. No more animosity. Married folks began to think that no spouse would be better than a spouse they have learned to loathe. They think the peaceful field is easy. They don't see the forest just beyond the field that they must pass through later. They forget how much they need someone to hold their hand.
If you are married, I want you to know that the grass is not greener on the other side of the fence. You made a commitment before God and many witnesses that God wants you to keep. Your co-worker or close friend is not your spouse. Though different, they have just as many problems and weaknesses. If you hop the fence you will find the ground muddier than you thought it would be.
The grass is actually greener on your side. If it is not, it is because you have not cultivated it as you should. Think about it. You can only work the ground on your side. You can only plant the seed on your side of the fence. God will help you to grow what you have sown. He can change the soil. He can do what you think is impossible in your field if you let Him.
Paul wrote in Ephesians 5 that married couples are one flesh, and that they should nourish and cherish their relationship. This means submission to one another in the fear of God. This means learning to be unselfish. This means making sacrifices like Christ made for the church. This means the washing of water by the Word.
If we will search deep within ourselves and look at our spouse again in the love of our vows, we will remember where our happiness has its brightest hope. We will see where the grass in truly greener. It is greener with them alone, in God.
"The Lord is my shepherd; I shall not want. He makes me to lie down in green pastures; He leads me beside the still waters. He restores my soul..." ~ (Psalm 23:1-3a)