Cinco de Mayo Assembly

I can't believe it! I  performed at my school's cinco de mayo assembly! It was so nerve-wrecking. I was really nervous because I'm singing by myself with a guitarist. It was so much different from last year, when I sang in a group with an instrumental.
This year, I decided to sing Bella Traicion by Belinda. It was nice to sing the song with a guitar instead of an instrumental. The guitarist, Jose Luis, is an awesome guitarist and learned the song pretty quickly. Thank you, Jose Luis. You're such a good friend for playing with me and performing in front of the school.
Before performing today, we practiced a little bit. I recorded it and it sounded pretty good. Everyone said it sounded good, even him. Maybe they're just being nice, but hey, it's the assembly and you don't want to bring people down before  a huge performance. I asked him if he really wanted to play guitar with me, since I could sing acapella instead if he didn't want to play, and he said he wants to. He likes to play. So, we practiced and practiced. It came out pretty decently.
We perform twice, since the school is divided in half when there are assemblies. It was a big hit the first assembly. Everyone got into and started clapping along. It was amazing. However, at the 2nd assembly, people didn't clap along except for some of the people in the band. They were nice.
Overall, it was a great assembly and a lot of people complimented me. It was totally different from last year. It's also totally different from playing cello in an orchestra. For right now, I have a recording of me singing BEFORE the assembly. Once I have the recording of me actually performing, I'll show you guys. My friend recorded it and I have yet to receive it. Hopefully, it will be tomorrow. 

So, have you guys ever been nervous before a performance?
What do you do to calm yourself down before performing?