This is an interesting question. There can be an element of grandiose thinking as part of bipolar. But the thing is, do you believe you are prettier and smarter than average because it's actually true? You've been told that many times (e.g., high grades in school perhaps or an excelling in other areas due to other intelligences; or being told you're very attractive with some frequency) and have independent confirmation? Or you simply hold this belief because you suspect it is the case?

In the past I excelled for a decade in a semi-professional group activity and wanted to branch out into another area, a related field. I set the bar high for myself considering I was known as one of the best in my North America doing the activity, I wanted to be one of the best in NA doing the related activity. My husband and I discussed this recently. Was this an expression of grandoise thinking related to bipolar? Or was it "the arrogance of youth"?

I don't have the answer to your question but wanted to share that it is something I grapple with too. An interesting question to mull over.