Love is not static. We grow dissatisfied and move apart; affection returns and we pull together again. Some people, ignorant of the process, pull away when the good times end and assume the bad times will last forever. These people flee, mope, or drift into affairs. Others see the ups and downs as part of a dynamic process, which, when anticipated and understood, can enrich and revitalize their relationship, even give it an added punch.
Janis Abrahms Spring has the following books quoted on Quodid: