No, Narcissistic people don't believe they have anything wrong with them. That's kind of its definition.
And, actually, it would be ignorant to say that we are Narcissistic sometimes because there's a difference between Narcissism and Pride, though, they are linked.
It would be more accurate to say: "However, it would be naive and ignorant to say that we're all not a little proud every now and then." This is normal and healthy. It is not healthy to be Narcissistic "sometimes." Though, I believe you can't be Narcissistic sometimes, you either are or aren't. I wouldn't know, I haven't taken Abnormal Psychology yet :/