You see the world through an intermediary agent which is a thought. Your thought tells you what it thinks is happening. When you are angry, it is because your thought tells you that something or somebody is doing something you think is wrong. But what is actually happening is a completely different thing, just as a restaurant menu is different from the food itself. Just as you you do not always get the food you expected from what the menu said, what happens is not necessarily the way you think it is.
As you become more aware, typically through learning and meditating, you gradually begin to see the event you call the thought itself, the neurological event, using your mental sense, just as you see and hear through your so-called physical senses.
At this point you find yourself aware of reality including the thought event and also your emotional response. You know you are not reacting to reality but to the thought. This knowledge can help you stay calm in apparently difficult circumstances.