Girl told me persistence pays off?

I still think about this one girl that I dated for a short while a little over a year ago and my female friend is like well why don't you message her? It never hurts to be persistent. I forgot how she worded it. I don't know opinions? I think after a period of time it just becomes desperate even if she is the girl that's ever made me the happiest.
Girl told me persistence pays off?
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