Treaveth,
Everyone has said it ALL BUT
In addition to what has been said,
Your "packaging" matters a lot.
Your "branding" must be solid if really you want to compete well out there.
Go for best of the best of things in your capacity whenever you go for interviews.
Dresses, looks (look very clean, shave the shavables) etc are very important.
My best days are Interview days, those are the days i feel more relaxed.
On those days, confidence keeps mounting and mounting (esp if i m on my well-tailored suit) but i don't allow it to Overwhelm me.
I wish you Success in future Interviews