I agree w/Parker.
From what I've seen a lot of times it stems from the person feeling like their needs are not being met by the other.
According to Dr. Willard Harley, author or "His Needs, Her Needs," from his information gathered from counseling thousands of men and women, he discovered that most women have five major emotional needs.
They are:
1. Affection.
2. Conversation.
3. Honesty & Openness.
4. Financial Support. (don't get mad Jag...its
most women..not all women according to Harley
)
5. Family Commitment.
Just FYI he believes men's major emotional needs are:
They are:
1. Sexual Fulfillment.
2. Recreational Companionship.
3. An Attractive Spouse.
4. Domestic Support.
5. Admiration.
In addition Gary Chapman, the author of The Five Love Languages believes in 5 main "Love Languages" or major needs that are universal to men and women.
They are:
1. Quality Time
2. Words of Affirmation
3. Gifts
4. Acts of Service
5. Physical Touch
His feeling is that each person has a primary Love Language that is most important to them and if they are not receiving that, they feel unfulfilled and may become disillusioned in their current situation and their relationship may suffer in many ways (including getting their Love Language filled by someone else).