This philosophy of I always hit it where my last thought was also applies to the full swing. If you are standing over the golf ball and you are thinking about the water or the out of bounds fence, there is a high chance that is where the ball is going to finish up.
Although this is not directly related to golf, it is a great philosophy on how to get good at anything. I also encourage you to watch the video below by Hank Haney on making 100 practice swings a day.
This is a great video if you want to improve your golf game
Bob Rotella is without doubt the most successful sports psychologist in golf.
I highly recommend his books
Golf is not a game of perfect
Golf is a game of confidence
Play the golf of your dreams