Posture is the foundation of your golf swing, so anytime that you are out of position, the rest of your golf swing will be too. Now, you can have some variations in posture, but THE most important element is getting down to the ball. It is critical that the bend in your golf swing comes from the hips and not the knees or shoulders. Simply getting into this position will help with ground force, load and rotation.
Check out the video below for a great drill on posture.