The pressure of your grip is critical. Not only for control of the club, but to generate max clubhead speed.
Grip too tightly and you will not be able to hinge properly; valuable clubhead speed and control will be lost. Grip too loosely and you may lose control of the club during mid-swing, accidentally sending your club flying and knocking your buddy across the head.
Try this test to help you FEEL the proper amount of grip pressure for YOU.
Hold the club at a 45-degree angle. Your grip should feel firm enough to control the club, yet loose enough for proper hinge with relaxed arms and shoulders.