A thought is often original, though you have uttered it a hundred times.

An idea can be genuinely yours even when many people have had it before. Originality is not about being first; it is about having actually made the journey to the conclusion rather than picking it up ready-made. The same sentence means something entirely different depending on whether you worked it out or repeated it.

Notice which of your firm opinions you arrived at and which you inherited. Take one of the inherited ones and try to rebuild it from scratch, or else let it go. And do not be put off making a point because somebody else has said it, since your version has your reasons attached.