Any tips on pacing urself correctly, and dealing with stress

On the 8th grade shsat test, I totally fucked up, stress completely took over my body, i blanked out on math and reading, i forgot how to subtract. Everything I read turned to dust minutes after reading it. It was the worst nightmare in real life i ever had. I blame stress for screwing me over, and i don't want to repeat this hell, so do you guys have any tips on pacing yourself and dealing with stress before during and after the shsat?