Night out/Party

I have a party tonight, and it's my first night out since the beginning of last month and I'm really really nervous. I feel really sick and I can't shake the nerves at all. I get like this before going anywhere like school or work. But I get it more so when I'm going out.. Is there anything I can do to stop myself from feeling this way? Because I'm losing my appetite and if I don't eat, I'll be a mess later on. Help meee (I wasn't sure which category to post this in)