This is something I've always done before a test, exam, interview, etc. and it helps me: remind yourself of what it took to get where you are, all the obstacles you've successfully overcome, everything you've studied and learned, and how capable, skilled, and wise it's all made you as a result; and also how lucky they would be to have you! It also helps to remember what sets you apart -- literally everyone has something no one else does, no matter how big or small. "You have all the weapons you need -- now fight" is a quote I read years ago which summarizes all this and it genuinely helps to repeat it to myself before stressful assessments
sorry for the rant, I hope this helps!!