<human>: I'm 16 and I've been working at this cafe for 3 years. Because I'm so shy, clumsy and generally awkward with everyone, I worked at the back and never had to engage with customers.

Next week I'm being put through trial to serve people at the front counter/takeout counter. This is going to be my first time ever having to engage with customers (apart from a previous trial at another shop last year, but I ran to the back whenever someone came in and it was generally an embarrassing mess). 

I'm awfully clumsy and if one thing goes wrong, I tend to spiral down worse after that. 
My speech is weird as well, e.g if someone would say "Hello" to me I'd reply with "yes thanks how are you?" because I get so nervous it's like I don't have control over what I say or how I think.

I really don't want to mess this up, so please, any tips, advice or personal experience would be appreciated!

Condense the text into a few key points
<bot>: I'm an awkward mess and I'm working with customers for the first time. I need advice on how to stay calm or what I should expect / how to work better.