To test this, try to be silent for 5 seconds. In those 5 seconds everything disappears which isn’t real to you, including your thoughts. But we are so identified with and amazed by our thoughts, that it doesn’t occur to us that our thoughts are not our thoughts at all.
If you do not identify with your mind but just live as if thoughts were guests who come to visit you, you can learn to deal with them and stand above them. If you receive guests, would you let them take over your entire household? That is exactly what we do.
Thoughts meander where they will, carrying our passive attention along with them. Like water running down a mountain stream, thoughts running on autopilot travel through the spaces of perception, randomly triggering associative links within our vast storehouse of memory. By itself, such associative thought is harmless. However, our tendency to believe in, act upon, and drift away with such undirected thought keeps us operating in an automatic mode. Lulled into an inner passivity by our daydreams and thought streams, we lose contact with the world of actual perceptions, of real life.
Once we realise that thoughts & emotions are not us, just things happening to us, we are taking a huge, positive step towards freedom. The more you let go of them as they occur, the less power they have over us, and the more they start to disappear. The more they disappear, the calmer our life becomes, and the more you become our true self.