After a break up your friends may advise you to forget your ex and move on. But at that moment you feel that wish we had never broken up then this means you still love your ex. In this case getting your ex back should be your priority. Vanishing away from her life is the best way to make her feel that she has lost a major part of her life. Figure out your mistake which led to the break up and take a lesson from it. After a few days have passed initiate a conversation with her and then some day propose to your ex after resolving all your issues.