I hereby claim the copyright on a new term I've coined: 'The Spacer'.
The Spacer is the guy that gives you courage to break up with the guy you've been in a long term relationship with that you have long fallen out of love with. He is never 'The One' but generally sticks around long enough for you to make sure you don't get back with your ex out of boredom and gives you space to be single before actually dating the next potential long term or the love of your life. He can also help you realize the things you don't want in a man so you can identify what you DO want.
Disclaimer: I am not saying this is courageous but it works for those girls who cannot be alone and needs someone to cushion the break-up.