As a human being you have developed your own way of looking at things. You see the world through a filter or lens built up and fine-tuned on your beliefs and values. As such you only ever see your own reality, never reality itself. It’s taken you years to build up your own filter and because of that you’ll often try and hang on to it for grim death, sometimes in the face of overwhelming contrary evidence.

It’s not that you’re an unreasonable person because everybody is the same to a greater or lesser degree. Every single person has their own filter and has their own difficulties accepting that they are one of over 6 billion realities.
You can separate yourself from your automatic repetitive way of thinking though by asking yourself with a genuine sense of curiosity, one simple question.