Take a break. Do things that have long been postponed: repair, a trip to another city. Switch to Hobbies and socializing with friends. In the early days they will keep you from depression and melancholy, and then it would distract from the painful memories. Do not turn in on itself: you completely cover the memories and regret that it is impossible to return.
Don't look for right and guilty. If the breakup was accompanied by a scandal, so blame both of you. With time you will know which of you what is wrong, how this could have been avoided and all could. In the meantime, the psychoanalysis will not help: too fresh, the memories too vivid emotions.
Do not deny yourself small pleasures: visit cafes, cinemas and other entertainment facilities. They will also help distract you for some time.
Limit contact with your ex girlfriend. If you work together, then adjust your schedule so that "to interfere" as little as possible. You both are hard to get used to a new way of life, and the return of the old will exacerbate the fracture and the desire to return to the same rut.
Do not try to know how she's going through a breakup. Generally think less about her and not follow her destiny for some time until you calm down. Your feelings for her are still strong, so you will suffer from any information about it. If she's resting, meet others, enjoy life, are you more focus on self-pity, and the girl will accuse of all mortal sins. If she's worried about you, there is a desire to return to the previous relationship, even though they are exhausted and will not bring nothing but pain.
Take the gap as a necessary, albeit painful period in my life. You got apart everything I could, learned all I wanted. Life together would bring you more suffering or would not bring anything at all.
Pay attention to other girls. You are still beautiful, full of energy, intelligent, interesting beautiful to the opposite sex. Not necessarily start a new romance immediately after a breakup. Just give non-committal attentions to other women. The concern earlier you gave only one, now give others.