Although you are in a lot of pain right now, you must remind yourself to keep your calm and rethink the situation. The good news is, once you calm down, you will immediately realize that the situation is not as bad as you initially think. So that's the first step you should take.
Step 1: Calm down.
Don't make matters worse by worrying unnecessarily. Having some time away from each other so that you can think things through may not be such a bad idea. The important thing is to know how to make good use of the time while both of you are apart.
Step 2: Understand the situation.
One way to make good use of your time, is to think about the cause of the breakup. You can't really come up with a fix if you don't know where the problem is. They say that love is blind. That is true sometimes. Both parties are so blinded by love that even when something goes wrong, both choose to ignore the problem - until it's too late. Now is the time to reflect and think about the problem. You have time on your hands. There is no need to act rashly.
Step 3: Accepting the truth.
Let's face it. The truth can hurt. But if you don't face the truth, you stand little chance of getting back with your ex. Fortunately, most situations can be reversed. Things are usually not as bad as you think it is. Acceptance is the first step towards healing.
Step 4: Coming up with a solution.
Now that you know where the problem is, it's time to come up with a solution. In other words, think about what you must do to rectify the situation. Make sure that you are prepared to do whatever it takes to win your Ex back. Don't just make empty promises to yourself. If you do that, you'll probably be making empty promises to your Ex too. That will lead to another inevitable breakup, which can hurt you again.
Step 5: Taking action.
With a plan in place, take action! If you tell yourself you are not going to lose your temper from now on, communicate that to your Ex. Make sure you do that in a loving tone. Above all else, apologize for whatever happened - regardless of whether you are right or wrong. If you truly want to make up with your Ex, remember that there is no place for ego.