I go through phases where I accept/deny my diagnosis. Usually I'm in denial when I'm euthymic because I feel as though I don't need medication. "I'm fine, see? No episodes!"

Then when I get depressed or manic, I go back to accepting the diagnosis. It's only when I'm actually experiencing (or have recently experienced) an episode that I accept it.

I'd say it's not uncommon for people to accept/reject the BP diagnosis, especially if the diagnosis is new. For a lot of people, it takes years to accept.

What helped me was creating a chart with two columns. The left column was for why I think I had the Dx and the right column was for why I think I didn't have the Dx. It forced me to think through my symptoms carefully.