Stop duffing with driver?

This is exactly why the harder you try to hit the ball, the worse the outcome of the shot. When you try to 'trash' it, your muscles tense up, some exert more force than normal and as a result, your swing-plane is off on the downswing. Most likely you are subconsciously using a lot of your right arm. If you must swing hard, keep a swing thought in your head during the downswing: Level flight-path of the club head as you approach the bottom of your downswing. Thinking about 'killing' the ball will only cause you to hit DOWN instead of forward.