It’s impossible. The only way to avoid thinking of an orange is to think of an apple in its place. The only way to not think of a polar bear is to think of ANYTHING else instead.
I learned this lesson while powder skiing in the trees and forests of Whistler. At first I would focus on the trees; the thing I was trying to avoid. With predictable results. Then I had an aha moment. Look at the openings and spaces between the trees! After all that is what I wanted. To ski all that beautiful powder in the forest. In other words, focus on what you want and not on what you don’t want.
The same thing applies in golf. If you are standing on the tee and you're telling yourself: “don’t go in the water; don’t go in the water” I can promise that most of the time you will land in the water. Our brains’ can’t process the “don’t.” So our mind interprets our self-talk as “don’t go in the water.” The best way to avoid the water is to focus on a target that you do want. Perhaps the left half of the fairway.
Your self-talk matters. The next time you tell yourself “don’t forget” replace it with “must remember” and see if that gets you a better result.
Worry is another form of putting your focus in the wrong place. The next time you are worried about something, ask yourself this question. What are three things I can do that would make the cause of this worry to go away? Instead of the feeling of dread that comes with worry, you will experience an energy that comes from possibilities and solutions.
Or as Mark Twain put it: Worry is a complete waste of imagination, most of my life's worst experiences never actually happened.
In all things focus on the outcome you want and not the thing you want to avoid. The brain can't do a don’t; it can only do a do!