I noticed this effect when taking my PSAT, the week of my psat i had my sat as well so by the time by psat came up I was exhausted and just decided the day before the test to chill and relax. This effect of relaxing carried over to my test and I was so calm and did really well because of it. Would you recommend that before the sat to just relax maybe review some formulas and vocab but not to do any serious studying or stress out.