If your partner is having an on-going affair with another (third) party, it is extremely unlikely that any progress can be made in traditional marital counseling. The reason is because your partner will be too emotionally unavailable. Their dependence is being invested elsewhere and some of the necessary emotional ingredients for feeding your relationship will be missing. Meanwhile, most people in your predicament will be building up feelings of shame, whether on a conscious or unconscious level. If your partner has never exhibited deceptive behavior prior to the affair, then restoration of the relationship may be possible with professional help and elimination of the other relationship. However, if your partner’s deceptive behavior has preceded the affair, then the prognosis for improving the relationship is grim. If the latter case applies to your relationship, stop here and go to our explanation of relationships involving intentional deception. Even if there has been no history of prior deception, do not assume that cessation of the affair and the passage of time will together heal the relationship. Trust is usually not restored by the mere passage of time. Under the best of circumstances, a lot of hard work is usually necessary to create a new level of intimacy and a new awareness in your partner for why they developed the affair the way they did.
INTERVENTION #1 (If the affair may still be on-going)
Set up an appointment to see a counselor by yourself. You can then further evaluate your options with professional help for gauging their likelihood of success. You may also want to pick up a book by Maggie Scarf titled Intimate Partners. It clarifies some of the possible emotional dynamics underlying many affairs.
INTERVENTION #2 (If the affair has definitely ceased)
Talk with your partner and to determine their openness about the affair. If they are not defensive and seem to be be ready to reinvest in the relationship, then invite them to go together for a joint counseling session. If they are defensive and evasive, then arrange a counseling session for yourself alone. In the latter case, do not harass your partner to get them to go to counseling with you. You would probably only get their passive-aggressive compliance instead of full participation.