Why do I suck at interviews?

[Quintease]

I really do suck y'know. I have never got a job from an interview alone. In the interview I get nervous and I talk shit and I just talk and talk and talk...
I'm still upset about the interview I did today that I am utterly CONVINCED I screwed up, despite being referred for it by someone in the organisation.
There was a point, where I was answering a question and I realised I had actually FORGOTTEN the question she had asked me. D'uh.

My hubby has been assuring me that he would rather hire someone who is nervous over someone who is over-confident, but I think he's lying.

I have another interview coming up and it's REALLY IMPORTANT! How do y'all combat your nerves? How do you impress people with your knowledge and wit???