People are not happy because:
1. They don't put Christ first in their lives.
2. They're full of conceit, that is, self-centered.
3. Thoughts are centered on "make me happy", that is, the desire for the other to "make me feel good" is a priority in the thinking, rather than something more unified like teamwork.
4. Self-righteous attitudes lead to a commitment to always being right about everything, and this is what causes all the bickering on petty things.
5. "Falling in love" is all about the euphoria, so when it subsides to normalcy, it must be the fault of the partner. The euphoria is an addiction, so there are withdrawal symptoms.
6. The stress of relationship and caring for the family adds to the pressure to perform, which cramps the style of the free-spirited and lazy, causing their unhappiness.
7. The pressure to perform is increased when demands are made by the partners. There is often a "you're not doing your part" attitude.
8. Snap judgments are made from suspicions, and either there is building resentment from no communication, or the kind of communication on such issues causes conflict.
9. They have little to no discernment on what to tolerate and what not to tolerate.
10. The prideful attitude of "I don't need no help" causes them to reject any suggestion they need counseling.
11. Vying for control of relationship and family, that is, power struggles.
12. Ignorance due to lack of good education and leadership.
I'm sure this list could go beyond 100.