The only emotion I can ever recall feeling when staring down at an exam is abject fear as every fact I knew drained out of my head.
I was always a relatively bright kid, but never super smart. When I worked hard, I got top grades and when I slacked, I didn't. At some point I stopped working hard and drifted through education, getting a mediocre degree on the way (on the upside, I have great soft skills).
From discussions with other gifted people, I get the impression that most of them worked really, really hard, even if they didn't realise it. But I have heard the odd person who maintains it all came naturally. Is this you?