I realize this is a couple days too late, but I do have some tips:
4:00pm the day before the GMATStop studying! Anything you cram in at this point may do more harm than good. Incorrect answers can shake your confidence and add to your stress.
It’s time to create your test bubble. This is a sphere of peace and quiet in which you’ll remain until the end of the test. Give friends and family advance notice that any conflicts or problems will have to wait until after the test. Let them know how important the test is for your career and future, and ask for their help in advance.
6:00pm the day before the GMATGo for a walk. Eat a healthy dinner. Read a magazine or some other light material. Try to avoid screens (like the one in front of you now) for a few hours before bedtime.
Not too late on the night before the GMATGo to bed! There is no substitute for a good night’s rest. Of course, you can’t cure a chronic lack of sleep in one night. Hopefully you followed the advice above and started this routine several days in advance.