They'll Always Be an Option
Just because Rachel and Ross made it doesn't mean that every seperated couple are meant to be. Remember this is reality not a TV show, that's written to pull and tug at our emotions. Face it, there is a reason why the two of you didn't work. If it helps, make a list of the positive and negatives reasons of being broken up. Remember that if your ex is a friend, odds are that you will continue to justify the negatives and subconsciously make them out weigh the true positives. Remove the option of your ex by taking them out of your life.