Oh. Okay. I get what you're saying now. I think.
How do you define selflessness, anyway? To me, selflessness doesn't mean "being a doormat", and putting the happiness of your partner ahead of your own. In fact, I think that's worse than selfishness! Rather, I see selflessness more as being supportive of one another while doing something good for the world (e.g. raising children). It all goes back to compatibility, really; if one person is concerned with self-gratification and the other isn't, then the relationship fails, whereas if both are selfless and have a common sense of purpose, then the relationship is more likely to last. I hope that makes an inkling of sense.
As for whether the goal of happiness works... if you're still together 10/20/50 years from now, let me know and I'll promptly retract my statements.