Are you trying to decide whether to move on with your life after a break up or how to get back with your ex? Which ever you choose will be both difficult and will test your ability to overcome your emotions. Some people are able to move through this very easy while others seem to have great difficulty. Before you make any decision as to what you will do, think really hard about your choice.
Look at how things were with your ex and how things are now, which one was the better position to be in. Was your break up over some silly argument or was there a serious issue that the two of you dealt with. Was one of you at fault or can the blame be shared equally. If you are the cause of this break up did you apologize, maybe more than once.
If you had apologized before the break up it may not have had much impact, it may have looked like you were just trying to salvage the relationship. If you were to apologize after the break up it would have a different meaning. It would appear to be more from the heart instead of just talk.
If your ex was at fault then you might want to apologize anyway for the way things turned out. You may even accept their apology or better yet forgive them for their actions, forgiveness can go a long way. It's possible you may never forget the reason the break up occurred and if the two of you reunited is there a chance that it will always be in the back of your mind?
Show the other person how you have changed for the better and remind them of why the two of you got together in the first place. Show your best qualities and be the best person you can be. Getting your ex back will take work if that's what you want, but it can be done.