One Is a Lonely Number (1972)

A young woman has difficulty understanding why her husband walks out on her. Alone for the first time, she finds life difficult to cope with, and for a time, lives with the hope that her husband will come back to her. After uncovering disturbing new information about her husband's infidelity, she finally comes to realize her marriage is truly over. And it is only then that she discovers what is truly important in life.