Every situation is different. At your young age it's certainly more likely that you could convince her to come back, but you have to question whether that's what you really want. If you feel like you've said all that can be said, there's little to be done, I would think.
It's normal to miss your ex-girlfriend at first, if you didn't really want the relationship to end. Try your best not to obsess over her, but only two days have passed--this wound is still fresh. Give yourself some more time to think, clear your head, and perhaps gain some detachment.
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The machine does not isolate man from the great problems of nature but plunges him more deeply into them. -Antoine de Saint Exupéry