It can be difficult, but it is important to take time and reflect on what went wrong with the relationship, on your side and hers. Figure out what you liked and didn't like, take responsibility for yourself, and recognize that a breakup is a powerful and motivating opportunity for growth. Establish some discipline in your life; create a solid routine, exercise, read, get ambitious about a career, etc. Serious change won't happen immediately, but as time goes on you'll start to notice the differences in yourself and in the way your future relationships play out.