Practice to get Better
The Pendulum Drill is a great way for you to understand how the weight of the club head works in the golf swing.
Another video of the Pendulum Drill. Just pull the butt end of the club towards the target in your downswing and this will cause the double lever in the pendulum to create a tremendous amount of effective club head weight and cause the whipping motion in the swing.
Practice with a Purpose
Amateur golfers have difficulty taking their swing from the practice range to the course. This is mainly attributed to failure on their part or negligence to practice the same way that they play. Golf is a target game. When playing, you need always to have a target and focus on it rather than on the mechanics of your swing. And you need to do the same to make your practice time more effective.
Better yet, practicing playing target golf on a driving range makes it easier to be target-oriented on the course. This also saves you from struggling with taking the style of playing you practiced on the driving range onto the course.
Always aiming at a flag or other objects on the practice range will dramatically improve the accuracy and consistency of your shots on the course. No matter what part of the swing you work on, or whatever swing problem you are trying to fix, your mind's eye needs always to be fixated on your target.
No doubt, it's always good to hit with your favorite club when you fix your swing faults, but you'd better practice hitting all clubs in the bag to be a versatile player. Hitting with your favorite clubs and shots only robs you of the chance of improving your versatility and confidence.
Of equal importance is practicing your short game. Amateur golfers tend to only practice the long game, but to boost your confidence or rather to hit your approach shots comfortably with less effort and anxiety you need to have confidence in your ability to play around the green. With a good short game, you will always have a better chance of achieving pars or birdies.
To be a consistent ball-striker, you need to develop and stick to a good pre-shot routine, which you need to use for both practice and playing. The routine used for practice needs to always be the same as that used during a round, and vice-versa.
Stop just hitting balls at random and try to make your mindset during the practice session equal to that of your actual play. This, in turn, will allow you to stay in the present and concentrate on the shot at hand. It will also help drive negative thoughts out of your mind.