For every thought or emotion there is a related physical response.
If you are playing badly and find yourself slipping into negative thought patterns, you may find it difficult to improve your game, especially if your negative thoughts (self- talk) lead to emotions which cause muscular tension. Negative thoughts also break concentration, possibly leading to rushed shots and poor course management decisions.
Think of it this way. Let us assume that you start every round with the ability to produce your best score ever. What happens is that various factors conspire to reduce your potential before and during the round; these will include, self-doubt, poor shot selection, rushing, anger, muscle tension, bad luck etc and your final score will reflect your ability to overcome these external and internal interferences to your performance.
So how do we overcome that negative self-talk which can interfere with our potential? Well, the first step is to recognise your negative self-talk. e.g. you idiot, you're hopeless, why do I keep playing this silly game? the greens/tees are awful, don't like playing in this weather etc.
This Works!
Do this for the front 9. During your next round, notice when you have any negative thoughts and write them down or remember them. Don't try to stop the thoughts at this time, just try and notice how or if they affect your game. During the back nine when you notice the negative thoughts stop where you are and acknowledge them. Then think of an anchor word (a positive, abstract word is better as this will break the negative pattern more effectively, e.g. "Calm", "Stay Cool", "Smooooooth") and decide that this anchor word will clear any negative thoughts. Say or think of your anchor word and carry on playing. Like anything new this may take some getting used to but if you stick with it, it will give you more control over negative self-talk and improve your game.
This Works!
When you are on the course and you hit a poor shot it is pretty much guaranteed that you will give yourself a hard time. "You always hit it there on this hole" "I'm not playing well today/ It's not my day" When you get these negative thoughts imagine that you have Steve Williams (Tiger Wood's caddy The world's best caddy) carrying your bag. What would he say to you if you hit a bad shot? Talk to yourself in the way you could imagine the world's best caddy talking to you when you are not playing at your best. This should not only improve your performance but you will definitely find your stress level will be lower.