Perhaps you might suggest that she try to think of the times of abstinence as times of anticipation. We often have periods in our lives when we delay fulfilling our desires in order to make the fulfillment of those desires all the more special. For example, we often place presents under the Christmas tree for weeks before Christmas Day in order to enjoy the loveliness of the packages, to speculate about what’s inside, and to enhance the pleasure of opening them on Christmas. In a similar manner, through NFP you and your wife have the opportunity to anticipate and enjoy Christmas Day every month of the year.