Vastu principals are based on 8 directions,and balancing energies of 5 elements of nature. e.g:-
-If someone sleeps keeping their head towards north, they may not have sound sleep. Because north & head of human are positive poles. Thus positive + positive poles repel each other and lead to disturbance in sleep. So in Vastu, directions are most important to keep one healthy and prosperous.
-Similarly, if we place the water in place of fire then the fire will not burn. Because the south- east is the direction of fire and if we place a water point in this direction it will hamper health & prosperity.