This is a theory of mine that I think many couples can identify with (I have seen many go through this so i know). It is a theory that says that one is not really happy by oneself in a relationship. They feel that since they are in a relationship they must feel the same level of happiness, sadness, anger, desire etc etc at the same time, all the time. Though they know that it is not possible they cannot give this thinking up (what is a relationship about then?). So to maintain the power balance in the relationship one falls back on the simplest and oldest way to be happy. Relative happiness.
How it works is simple. If you find the other person looking or feeling genuinely happy, or even remotely happier than what you are, you instantly feel unhappy. You give out a response that is a fitting reply - how can that person be happy when you are not? Your powerful reactions instantly dull that person's happiness. The smile fades, the laughter subdues, the demeanour becomes sombre, the spirit dies and life ebbs in deference to the violence or venom in your response. A look, a dull response, a sharp retort, a banging door, a phone that is cut off midway, a change in the tone...any number of those happiness-eaters are thrown at you. When all traces of your happiness, which you have gathered carefully elsewhere (how dare you?), are wiped out, then the other person is happy. Or happier. Relatively.
Then comes an olive branch which may be taken reluctantly or whatever, but overall the happiness balance is maintained. The corollary to this is that no one can be happier than the other. Or, the happiest a person can be is limited to the highest amount of happiness that exists between the two.
This is not about men or women - this I find is universal in couples. Everyone finds a way to lessen the happiness of the other to find their own happiness. Rarely do we find anyone able to manufacture their own happiness and be content in that. These rare people are also those people who enjoy seeing other people being happy too.
Some people live their whole lives being prisoners to this relative happiness principle. Prisoners of the others responses. Their entire life is spent prying on the other person's life, their sources of happiness and cutting them off, so they feel happier. They have no life, just a reaction. For these people it is apt to use the phrase - get a life! It is unfortunate that they cannot find the courage in themselves, the self-esteem to find something worthy of their attentions and having to conviction to be happy with it.
Happiness does not come from the outside, from another person, from things. It must come from within. One must find the pleasure in the small things that make one happy. It requires honesty, love. If books give it to you so be it, find your books. If exercise does it, so be it. If solitude does it, so be it. Find your small pods of happiness and live that, be that. When you find that you can be happy by yourself, you find that you don't need relative happiness to be happy. Your happiness is your own and it spreads like a wave. On the other hand relative happiness, reduces the overall happiness in the world. Go, find your happiness in the things that make you happy, not in things that make you unhappy. And make the others even more unhappier.