Tension is a real killer in a golf swing and it often times starts in your hands.
If you get the club resting too much in the palm, what is going to happen is when you try to make your golf swing your wrists are not going to hinge properly unless they come off the golf club. You will end up with a short backswing and you will tend to let go of the club because the clubhead is heavy and it will end up falling off at the top of your swing.
The next step is to grab hold. Hold tighter. You feel like you are controlling it but then you have no wrist hinge. Not only that, the tension that you create in your forearms goes all the way up your arms and into your shoulders and your whole swing starts getting locked up. Your arm swing is not free anymore, you do not turn your shoulders as well, everything starts getting more tense.
I can not stress enough how important it is that you get the grip down in your fingers of both hands so that you are able to let your wrists get activated in your golf swing, either naturally or when you are intentionally trying to cock your wrists so that you get the power source that you need. Your grip is going to help you. Use a good-fingered grip.