Did you just get the proverbially "relationship boot"? If you're thinking about trying to re-establish your lost love then you need to feel comfortable with making a few personal changes and asking a few questions.
Either your ex wasn't getting something from you or you were doing something wrong. Try to establish a dialog with your ex, find out what they needed (or did not need) in the relationship.
Hearing criticism is always hard, but keeping a "cool head" will allow you to move forward with re-establishing your relationship.