1 Corinthian 7:5

Defraud ye not one the other, except it be with consent for a time, that ye may give yourselves to fasting and prayer; and come together again, that Satan tempt you not for your incontinency (KJV)

Then: Here's the exception - Paul's "Let me be clear" statement. Priority always goes to serving the Lord. There are times in an individual's life where fasting, prayer, or other service to the Lord must take priority over the marriage. The marital relationship is never above that of the one-on-one with Christ. There is time and place for both - in their proper order. Whenever that order is pre-empted Satan takes over.

Now: Without thinking about it, many couples fall into the trap of letting marriage issues always come first before Christ (or at the other extreme, they always come last - even to the point of being ignored). It could be a matter of miscommunication, of keeping an individual's relation to Christ too private, or an actual problem of priorities. Prayer and fasting over the disconnect can solve the problem and make our ways straight before the Lord.