This is the reason people meditate. People have the ability to imagine stuff that doesn't exist and may never exist or existed in the past. Think about how easy it is to remember some traumatic event from the past. Dwell on it and begin reliving it, feel the sensations as if you are present at that moment. Meanwhile, back in reality, you are safe and warm, sitting on your couch. This way of thinking is extremely common and is the gateway to depression.

Meditation works by resetting your biases so that you notice what is going on right now. It's like a universal solvent for the mind. Don't get me wrong, thinking is important, as a source of creativity, organisation and planning. It's not like you can ever stop thought but it can become extremely toxic to your mental health.