Good luck tomorrow! Be yourself and have fun.

I used to do seminar-type teaching at undergrad. level. In that kind of discussion group scenario, if you're lucky the conversation will flow organically... and if you're not, it's your job to think of something to put to the group. An ex-tutee once congratulated me on my powers of devil's advocacy, but then I taught moral philosophy, in which 'But what's wrong with stamping on babies?' is a typical enough enquiry...

"GOG help me" as in "♫ GOG save the Queen, she ain't no human being ♫"?

While I'm not a teacher proper, as an "IT assistant" I frequently try to teach the teachers how to use their computers*. Does that count?

* In as many cases as possible, I have them sit in front of the machine and then instruct them on what to do, rather than doing it for them. Sometimes they even remember what to do the next time.

Yes, I made it through my first day! Of course, now the real fun begins since I need to introduce my students to the actual subject material. I expect that I'll feel more comfortable teaching by the end of the week, but I'll probably feel just as exhausted XD

Best advice, this can't be emphasized enough. As Savielly Tartakower famously said: "I never defeated a healthy opponent."

Well done then ; )

I'm so very tired...

How do you other teacher folk work like this for 5 days a week, for most of the year? What tips do you have for keeping your energy up?

It gets better later on. One of the things that will take up significant time when you start is creating your notes for the lesson, but assuming you don't change teaching subject, you can reuse the same notes in later years. So while you'll still have the same other things to organize, the notes creating time should be reduced.
Just hang in there, it will get better.

Salty water.

I remember after my first week my feet hurted so bad that i almost cried. Someone suggested me to keep my feet in salty water after shower when i come from work. It helped a lot for me.

During my college we had a electronics class which was boring to us (since we were cs people and frankly didn't understand why we had that course) and 3-4 people started throwing paper rockets at each other. One of them ended up near the professor and he thought it was thrown at him. Then he took out his anger on the whole section by grading us all really bad at the end of semester. I just hope you don't do that, if someone does something objectionable hold him/her responsible to it, don't make everyone suffer for the actions of few.