Is there such a thing as a good break-up? Not really, if it is viewed from the perspective of the person with whom one is breaking up. There are, however, things to avoid at all costs and things that one can do to make oneself feel better. First off, acknowledge all the negative feelings that this is creating. Wallow in your despondency for a given period of time (not to exceed 3 months). You can play Aron Neville's "Everybody Plays the Fool" or Bonnie Raitt's "I Can't Make You Love Me" nonstop until the despondency/negativity gives way to some other emotion. Trust me, if you give free rein to your feelings, they will ultimately change.
Second, don't forget to eat and take care of yourself physically. That weight drop may look attractive, but it is really unhealthy. Connect with other family and friends who care about you. When you need an ear to listen, go to people who will do that for you. If they cannot show the care, concern, sympathy, and support that you need, get it from other friends/ family who can.
Third, stifle your pride about being "dumped." Whether long-term relationship, marriage, or short sojourn, it happens to just about everyone at some time in their life. True friends know that this is hard on anyone's ego.
Fourth, distract yourself. There is a fine balance between trying to analyze what went wrong to learn from it and obsessively going over what one could have done differently. Dwelling on the departed beloved is counter-productive. It helps to tell oneself that this person was obviously not "right" for you or that building a future with them would be a mistake based on their current behavior towards you.
Fifth and finally, love yourself. Don't devalue yourself based upon all the negative feelings an unanticipated break-up will engender. Time is your friend and this too will pass.