Evolution is a harsh mistress. Humans are meant to pair up, be husband and wife, and that is fulfilling. But it doesn't necessarily make either of you happy, and today's society says that being unhappy is grounds for tearing it apart. And as a man you get to bear the brunt of the consequences when that happens. Unless you're sure she is willing to truly commit, "for richer or for poorer, in sickness or in health, until death do you part", remember that you may wind up shouldering that burden. But if you're not willing then something will be missing in your life. It's a catch 22 and a difficult decision.