First of all to win your ex back you're going to need to come up with a plan.
You're going to need to organize your thoughts as well as your actions.
One: Agree with your partner that you think some space between you or going your separate ways is probably the best thing for both of you at the moment.
Now this is not going to be easy because this is not what you really want.
However it is necessary because you need some time to clear your head.
It's important that you be able to think clearly, so some time alone will give you that opportunity.
Two: It's important to take the break up calmly, I know it sounds crazy but trust me when I tell you that begging and pleading for your ex to take you back doesn't work.
In fact it will only make them want to stay away from you even more.
Also do not call or text your partner a hundred times a day, follow them around town or show up at their job like a stalker, these are acts of desperation not to mention you're making a complete fool of yourself.
I don't mean to sound harsh but I've been there myself so I know from experience.
Believe me it's not a good feeling when you want someone that doesn't want you.
Do yourself a favor and go out with the girls or guys and have some fun.
Although you may not feel like you want to at the time, it'll make you feel better in the end.