Winging It

I've been struggling, a lot, lately, with things which normally come naturally to me.
I've found these newfound struggles crushing.

Back on January 31st my choir began rehearsals for a concert which is this evening.
My conductor decided that the second sopranos could use a little more somethin' somethin', and so she asked me to sing that, as opposed to the part I regularly sing, which is first.
It scared me because I have a lot of trouble hearing inner parts.
Let me rephrase that. I can't hear inner parts unless they are substantially louder than the outer ones.
In the past where I've had to do a few lines of second, I have rehearsed it into the ground by how it feels, completely turning off how it sounds in my head, because I can't listen to the outer parts and sing the inner ones.
I know this sounds like self-defeatist talk, with all the "I can't," but I have tried for many many years to learn this, and have consistently failed at it, but it was never a big deal.  I have never particularly needed this skill.  When it came to ear training I could build the outer parts and then experiment with the inner ones until it had the same sound.  It isn't that I can't tell the difference between an f and a g when sung between a b and a d, it's that I can't find it if I have to sing it, and can't tell you which it is without recreating it on a secondary instrument.

So, like I said, I was terrified when my conductor asked me to sing second, but I'm a "can do" kind of girl, and I said "yes ma'am," moved myself to that section, and set out to listen and try to figure it out.

I missed a couple rehearsals. This is not like me, but roads were impassable one night from the village in which we live and the city in which we rehearse and perform. I missed another night when I passed out early in practice (ouch) because I was coming down with a nasty bug. Another night I was stuck out of town on an impromptu business trip from Hades my spouse made me go on after rescuing my niece who had been abandoned some 3 hours from home, yet near where spouse had appointments, and halfway to the appointments for the next day. Fun times.

So, instead of freaking out, I worked on the music a little more than usual outside of the house.
Let me rephrase that. I've spent hours working on the music. I have tried to sing it with various youtube performances of it. I have played it on the piano into the ground. I have written in counts and Solfege and notated intervals of concern.

The performance is tonight. I just finished another hour and a half of practice time. My toddler now knows the song that gives me the most trouble.

Here's the problem. I don't.

I still don't know it.

I. Do. Not. Know. It.

I have never felt more incompetent in my life.

Sure, I kind of have a working knowledge of most of the pieces, but I do not know them. Every time we rehearse, or I sit down to play another it feels like the first time, and I feel like I'm sight reading. It's like the final exam in a class you didn't know you were taking nightmare.

So, what am I going to do? I'm going to wing it.  I'm going to have a little faith in how neatly I've shown myself where I might be able to hear the notes I need to find ahead of time in order to sing them later.  I am going to mouth it when I don't know where we are.
I am going to smile and fake it.

And then I am going to strongly consider resigning from the chorale, because after the many hours I have cried over not being able to learn these super easy Handel pieces, after the panic attacks at the thought of tonight's performance, I don't want to put myself in a position to end up feeling this incompetent ever ever again.

Nothing is worth it.

Any last minute advice for winging it?