Some folks look at guns as complex tools that require as much skill and practice as piloting a helicopter. When you break it down, there are only a few points where human and gun interaction occurs: the stock and where it touches the body, the sights or scope and how the eye looks through them, and the trigger.
The trigger is the most important aspect of the human/gun interface. This should be obvious—the trigger is what makes the gun fire. It is the button that is pushed to send the bullet towards the target. If it is not activated at the exact moment the sights are aligned on target, the bullet will stray and the result will be a miss or a bad hit.
You can hold a rifle a number of different ways, use a variety of sights and even look at them with either eye and still get hits. However, if you booger up the trigger pull, no amount of prayer, chants, incantations or wishful thinking will turn the bullet toward the intended target. The key is to start with a good trigger.