Answers for Alison...

A few questions asked, a few questions answered:
Nerves.
I never used to have them when I was younger (I'm talking high school here). It was only as I progressed and got to a certain 'level' that I started to realize, wow, THIS level may have something to do with my NEXT level. It was my first year as a resident artist (in a program connected with a grad school) that I realized, ONSTAGE, in the middle of the Act 1 duet, that woah-- I hope this goes well so that the next and next and next thing go well.
And My heart was beating so hard that what it sounded like to ME was that my voice was shaking too.
I felt like my larynx was going to shoot right out of my eyeballs, and everything became really thin and weird in my head.
What could I do? I was in the middle of singing, so I just kept going. What seemed like an eternity later, which was probably less than 2 minutes, my mind stopped wandering, I focused more on the character and less on the 'sound' that I was trying to hear...and then it went away.
But almost EVERY show since that show... I've been calm on the outside and nervous on the inside (inasmuch as I can't control how my heart beats before the show starts)...then as SOON as I get onstage, I am in character and there is nothing that can freak me out...and even if I start to have that 'freakout' feeling of raised larynx I push myself MORE deeply into the characterization (the "acting"), and then it's gone.
And sure enough, when I listen to that clip from grad school- you can't.even.tell that I was freaking out vocally.
So it's a mental thing. And yes, it feels like it's affecting you and that you can't sing one more note..and then, you just have to learn how to calm it down yourself.
It's something I still work on for every performance. Find the fun and the calm, and try to ignore that fast heartbeat and the 'oh man, this is really real' feeling.

On the days of shows I try to find a routine. Eat normal things and not some crazy spicy chicken sandwich (that's reserved for AFTER the show--1am from Wendy's...yummm). I go through my music (speed-through). I get to the theater early. I warm up a few hours before..all routine things to stay calm. I know my heart will start pumping faster right before the curtain and especially right before my entrance. But I try to think of 'good energy' and how I can use it for my character...and beyond that, just trust in the voice and the fact that I've done it before, I'll do it again, and as long as I love it...I'll keep at it.

Preparing for a piece.
Well, I'm doing this right now, and no, it doesn't mean I practice every day. I have gone LONG bouts without vocally practicing, but almost every day, I will do SOMETHING that is considered studying. Whether it's marking up a score with a highlighter, doing IPA, doing translations, going through the words to something I'm trying to memorize in my head or testing myself by writing them down on paper...it's a combination of vocal preparation as well as mental preparation.

Getting something into my body 'vocally' can happen at any time and for any reason...sometimes I study bits of the role every day (study, not sing..just play the melody and harmony)...sometimes I have to sing it over and over and over, and then it's there.
But by the time it's 'showtime', or, rather, first rehearsal time...it's always there. Sometimes "magically", meaning, I don't FEEL like I had to actually sit and memorize notes and words, and sometimes it was note-plunking and playing memorization games with myself on the airplane.

'Nothing to do' is very often misleading. The shows that I have to learn music for are not until March and April, but... if I do nothing now, I'll have a LOT to do later.
So I TRY to do a little each day. And when I can't take modern music anymore, I switch to going through my old audition arias. Or I listen to some things on youtube. Or I google what other roles I could be learning or singing or looking into...which always leads me on a 'rabbit hole' kind of online chase and ends up taking half of the day.

So yes, I have 'nothing' to do for a while since my next show is Magic Flute and I have already sung it (nothing 'new' to learn except some dialogue), BUT I do always try to think a bit ahead and somehow get some daily 'practice'-- vocal, mental, translating, listening..just being around the art.

Hope that helps!