Cheat like a coward or work up the courage to change your life and be happy?

I understand that divorce is hard financially and emotionally. Plus, its even worse if children are involved. It seems today everyone would rather cheat on their spouse rather that work up the courage to end it and find someone that makes them happy. If you are that unhappy in your marriage and want out then why not end your misery? If you start another relationship while you are married doesn't it become tainted?