After Googling for few days, I found this is the only question similar to my situation.
However, I just solved the problem! So I am putting my answer here to help anyone else searching for this issue.
Here is what I did:
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Open “Keychain Access.app” (You can find it in Spotlight or LaunchPad)
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Select “All items” in Category
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Search “git”
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Delete every old & strange item
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Try to Push again and it just WORKED