Deadlines and stress

Working under pressure is one of my main wesknesses.I have put as a main goal to stregthen my capacity to deal with pressure and keep myself cool in difficult and stressful situations.
My problem is getting more serious when I have a very limited time to react : I rush to finish the job before the deadline, I am in a panic that there is not enough time left and I cannot stay focus on giving my best.
Next month I will participate in a very difficult multiple choice test and an interview for a promotion. My question is how I could manage that stress and stay focus during the test and the interview and do the best I can.
Thank you