The third essential step is to accept that the relationship is over. This is no easy feat. Sometimes it helps to take significant, ceremonial steps to promise yourself that you will continue to accept that the relationship is over. Send your ex whatever things they have left at your place. (Don't make a plan for your ex to pick up their stuff, just throw it in a garbage bag and drop it off!) If you haven't already done so, defriend them on Facebook, stop following them on Twitter and, by all means, delete them from your phone! These steps can move you dramatically closer to acceptance, as they reduce your ability to waste emotional energy fantasizing about someone who is no longer available to you and therefore not a suitable parter.
If these steps do not get you over the hump, consider some form of group therapy. Break-Up Boot Camps and other forms of group therapy are extremely effective, as the absurdity of hanging onto an unavailable or otherwise unsuitable ex is incredibly obvious when you witness it in others. Participants can clearly observe the futility in another's efforts to hang on; such observation opens the door for them to gain dramatic perspective on their own wasted energy.
Don't give someone else the power to compromise your happiness; force yourself to take the triple A steps and you will be in a better position to get over your break up and, eventually, have healthier relationships.