Seriously. If you’ve said the same thing one thousand (or even a few dozen times) and you are not getting the result you hoped for, then who is the stubborn fool? You know that it is not the way to get the change you seek, so why are you saying it again and again?
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Try something new. Anything. Just something different.

Say it in a different way. Think about it differently. Write it. Read a book about it and discuss.
Be creative. You know the issue and people in the situation. Think of a new way to address the issue.