Be honest with yourself and stop:
Overcome your own desires and live by integrity.
Integrity is giving up everyone and everything for this rare jewel; I did what was right.
If you are not in a relationship with someone else...
If you are not in a relationship with another, please consider your vulnerability. Not you, you say? "If you think you are standing firm, be careful that you don't fall." (1 Cor 10:12)
Rather than living in misery and being susceptible to temptations, fix your marriage now. If your spouse doesn't want to, then be strong enough to insist. Make yourself heard. Clearly explain your misery, danger, and potential future. Involve your pastor, your spouse's family, your kids (if old enough), or whatever it takes. If you ignore the situation, it will get worse.
Falling in love is a process. Follow the process and you fall in love whether you mean to or not. Vacate or violate the process and you fall out of love whether you mean to or not. You can be in love again. Anyone can follow the LovePath at any time in life, no matter what state they are in now or what has occurred previously.
If you are no longer "in love" with your spouse, or yours spouse is no longer "in love" with you, act now, before it is too late.
Joe Beam founded Love Path International (http://www.lovepathinternational.com), an organization whose mission is to save marriage relationships even in cases of affairs, anger, dishonesty, loss of passion and other marriage problems. Joe and Love Path International provide marriage help (http://www.marriagehelper.com) to couples who are in danger of separation or divorce.