I think I may be done being nice to girls?

My whole life I have been nice and respectful to woman and girls. Now I don't see a point of doing that anymore. My girlfreind just recently broke up with me just because she wants to be single. I gave her everything, I was nice to her, I was respectful, I dinsobmich for her and yet she doesn't care about any of it. She just keeps saying that she wants to be single or to be "free". Now this has chaned my whole perspective about woman and how they treat men or at least the nice. I don't know what to do should I change how I am or should I stay nice and respectful?
I think I may be done being nice to girls?
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