I think this is pretty much a rite of passage for early-career academic librarians. The first time I was a finalist, I cratered spectacularly. What can I say? My dad was a factory guy and my mom was an office assistant, and I had never worked full-time in higher ed; I had no frame of reference for what is essentially a 36-hour job interview. I don't know if anything could have prepared me.
It started to unravel during the obligatory night-before dinner. For obvious reasons I don't want to get too specific, but ... At the beginning of the dinner, my potential colleagues were talking to me, then they started talking to me less, and then even less, and by the end two members of the party were going on like they were best friends who hadn't seen each other in ten years. We were at that restaurant forever too. The next thing on the itinerary was a quick driving tour around the city. When we finally leave they say they're taking me back to my hotel. I ask about the tour and one of them tells me they've decided to skip it. Next morning, it gets even better. I'm taken to meet the university librarian, who is on the phone. So I sit in his office while he talks... And talks...
Knowing more about academic jobs now, I suspect I might have been the victim of an, ahem, rhymes with schmake schmearch, if you know what I mean. I was clueless at the time though, and I freaked out completely and went into a death spiral. Every interaction was more cringe-worthy than the previous, and my presentation was a combination of library instruction, shame, unintentional comedy, and self immolation.
I left utterly humiliated. The only advice I can give you is, I went over it again and again and eventually started thinking about what was and wasn't beyond my control, and for the things that were, I thought about what I would do and say instead if I could have a do-over. My next interview, I nailed it. I worked at that institution for a little while then hit the market again. I know hold what I have to admit is pretty much my ideal position.