I was sitting in my psychology class yesterday, when the professor started talking about how dangerous the idea of "the one" is. He explained that:

Because people meet other attractive people at work, or wherever, they get attracted to those people. Then there is a "cognitive gap" where they can't combine the ideas of one person being "the one", and being interested in somebody else. They then rationalize that the person they are with might not be someone they are in love with, and then they act. He said this is especially bad for women, who have easiest access to sex, and the kicker: who are more likely to feel the need to rationalize their attraction to somebody who is not their partner

In conclusion, psychology acknowledges the rationalization hamster, and proves that our culture's ideas on love are dangerous to real working relationships.