Does anyone else have trouble adopting a professional manner?

So I have an interview coming up and I thought it would be a good idea to look up some interview tips. I stumbled across one video on YouTube where the career coach started giving example questions that could be asked and good answers for them.

All the answers were so polished and professional sounding.

To me and in my everyday life I don't talk like that but just plainly & commonly like anyone else e.g. how you would shopping at a grocery store.

Eveyone says be yourself during an interview.

If I were to try to speak so professionally & calculated, I feel like it would come off as fake.

How do you guys handle your communication for an interview?

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