The correct finish is a crucial component of your golf swing and making sure you carry on through to a correct finish is vital.
Many amateurs pay so much attention to the moment of contact with the ball that their swing ends almost at that point. They pay no attention to the finish. Their finishes are either cut short or so extravagant that they lose balance. A good feeling to try and develop on a full swing is that the stomach should be facing the target at the finish. The right shoulder should be closer to the target than the left. The finish is almost the opposite of the back swing in that your right arm should be straight and your left folded. Drill this into your subconscious and you will soon be making complete swings.
By consciously accelerating through the ball your arms will extend down the target line automatically and then swing the club up and over your left shoulder to the finish. Stop and think at the end of your swing and compare your position to that described in the paragraph above.
Compare your finish position with the position of the pros you watch on TV. Hold the position. Stand tall and proud and you will soon be watching a ball sail straight and true down the middle of the fairway.
I used to play with a very good scratch player who would finish his shot and hold the position for about 2 seconds. He would occasionally then drop the club and it would fall on the ground behind him. I asked him why he did this and he told me it was to remind him to finish the swing correctly.
Try and develop a mindset in which contact with the ball is a small event in the whole swing and not the end object of the swing. If you can ingrain a feeling that carrying through to a correct finish is the object in itself your golf will improve immeasurably.