Well here is a subjectively unsatisfactory answer and that is we simply think thoughts that others don’t think and then go about trying to convince those that didn’t think it (which is everyone except us) that it was worth thinking. Easy to see where the self doubt comes from and sure, there is an element of ego there. However, if there wasn’t, I’d have to wonder who all these thoughts in my head belongs too?

So I’d say you’ve found the right non-answer which is better than having the wrong answer.