Try to think for a second about why the breakup happened. It's tough to be totally objective about it, but get as close as you can. Try to remove your emotions as much as is possible. Think of the good times and the bad. How did you and your lover meet in the first place? What was it that brought you together? Are you truly meant for each other?
Reasons for getting back together.
Adding up the good things and weighing against the bad with a close to neutral perspective will give you good clues for deciding whether or not to try to salvage the relationship. If the good seems to outweigh the bad, then think about the reason(s) for the separation. It could be that your ex just needed some time to think. In that case, all you need to do is give them that time, then check to see if the sparks are still there and if it's possible to re-kindle the relationship! Of course, this would be one of the best outcomes, but it's not the only thing to hope for!
What is best?
If you were able to objectively weigh the pluses verses the minuses then you are getting close to the truth of the matter. Remember that you will not die without your ex. It could be that you find someone better someday! Then again, you've probably decided that you want to try to get your lover back. Keep cool, give it time. Be humble and lose your ego if you can, then move on to the next step. Try to get your ex back!