How can i calm myself before an interview?

Balanced breathing: There is one technique - sniff out your fear, the other technique - breathe through one nostril slowly and release through other side eg breathe through right nostril hold the breath release through left stimulates left brain - the other way stimulates right brain.

Propranolol can help: Performance anxiety of any type is often easily treated with 20 mg of Propranolol a couple hours prior to the anxiety provoking "performance". It is used in the business, entertainment and sports worlds on a fairly regular basis. Test how one responds to the medication prior to taking on the performance to be sure you tolerate it.

Relax: It help a lot to know what to expect. It is impossible to know what will happen but doing the "legwork" before hand allows you to feel more confident, relax and will allow you to came accross a better candidate for the job.