Negative thinking is a huge issue in all walks of life. The amateur golfers comment of " knew I was going to do that"sums up the poor thinking golfers attitude to the game. The 1st thing I try to do to interrupt this train of thought is to literally "look up" We always feel better when things are "looking up," when things aren't going so well we do tend to feel "down" and look at the ground or our feet. Check out the tree tops. Some Professionals would have a competition to see who could count the most birds. Our minds work very well with factual evidence of the things we have successfully undertaken. Be it a tough course, difficult hole or daunting tee shot.
I have seen Seve in his prime hit several balls of a tee in a tournament practice round because he felt he could not walk away without the image of a perfect shot. Other tournament players have different methods to help them stay focused and interrupt negative thoughts. Jeff Hawkes was famous for playing his practice rounds without striking a single ball. His caddy and clubs went round with him and he "imagined" the perfect shot for every hole. Very powerful stuff indeed. A negative thought can be quashed before a shot by following your ritual. By saying "be positive" or "don't think about it" simply isn't good enough.
We need tools keep us in the correct state. A negative thought for me is one that has taken me away from the present and either taken me back to the past or forward to the future. Not very useful. Meditation helps those of certain religions or beliefs. Simple breathing exercises to reduce the heartbeat can really help the golfer. Try to expel ALL the air and suck the tummy in. Then, rely on your instinct to breathe out. You can interrupt any negative thoughts by thinking of past experiences of success and the feelings they brought. Reliving them in your mind and playing them out can mean you rely on facts and not feelings. Thinking of poor experiences in the past can easily be deemed as negative. To keep away from this place, stay firmly in the present and stick to your ritual. This will enable you to intervene quickly if your mind wanders out of a calm or quiet state.
For me, negative thoughts occur quite easily and I have to bring myself to a calm state and employ my ritual to get myself back into neutral. Sometimes easier said than done but very possible if you follow the routine or ritual you have. If I give 100% to every shot and achieve my perfect ritual (or complete the circle) on every shot then negative thoughts are not in my head. My score is not always what I want, but the person I am is a much happier one.