Becoming an observer of your thinking.
When you begin to see thinking as thinking and not reality, you will begin to see that, thinking is no more than an illusion. You can begin to remove yourself from the thought. You recognise that just because you had a thought, it doesn't make it true. It is just a thought. You will become the observer of the thought. You don't have to stop the negative thoughts. You just have to begin to let them pass by.