The first rule: do not think about what others will think about you, even if your job depends on it. Don't be afraid to be ridiculous, just be yourself. Sincerity is felt by all people without exception.
Second: don't react to criticism. Make useful conclusions, but do not despair.
Third: mentally prepare for possible failure or negative reviews, this is the surest way to protect your psyche.
Fourth: imagine that you are not talking to a casting Director, but to a close friend or girlfriend in a familiar environment.
And fifth: use the breathing relaxation exercises which you've been taught at a theater School or acting training. For example, some actors and vocalists alternate deep breaths with breath holding and subsequent exhalation. Remember your yoga classes, there were also breathing practices. And do not forget to do articulation exercises before casting, warm up your speech apparatus.
Control your emotions is extremely difficult, but this is the skill of the actor. Practice every day, read at home in front of the mirror, sing in the shower and even talk to strangers on the streets!