Pixie Godd Luck - actually you dont need luck , I will give you a couple of tips.
Postitive thought - before you go visualise yourself being calm and friendly and answering all their questions, they like you and are impressed, you get the job
Being the person they want to employ - I don't mean lying here or not allowing your personality to come through, i mean a bit of acting to be a more confident person while the real you is going "oh no - I don't know what to say", the interview you is answering positively or asking to come back to that question later.
Prepare - think in advance about some situations where you did something really well, or where you coped with something that wasn't going well and what you learned from it.
I am sure that you will do well.
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