Many couples come in because one person has more sexual desire than the other. These couples believe that the person with lower sexual desire needs to be fixed. The reality is, it is hard to know what the real desire level is for the person that has lower desire. It is hard to know because low desire levels are more reflective of what goes on in the relationship than on the individual with lower desire. Most often, couples create dymanics that hold desire captive for the person with lower desire. Sex therapy for these couples involves become aware of this dynamic and making a commitment to change these dynamics. You can read about different dynamics here.