If you have been devoting your free time and long hours over the weekend to practising your GMAT, we suggest taking a break from the GMAT for 2 or 3 days before your exam and, to avoid additional tension, getting yourself in shape for the resistance that the test itself requires.
Before doing your GMAT, relax and do whatever it is that you do every day: have breakfast, read the press, and if you have time, take a stroll. The test will try out your mental readiness, and being in a good physical and psychological state will benefit you on exam day.
The most important thing is to trust the preparation that you have carried out. If you have worked in accordance with a serious study-plan and have seen that you have made progress over some three months, you could well be readier than you may think to do an excellent GMAT.