Negative thinking appears to be more abundant in our society than positive thinking. It seems that with most people, positive thinking requires some effort, whereas, negative thinking comes easily.
You view the world through your predominant mental attitude. If your thoughts are positive, that is fine, but if they are negative, your life and circumstances would probably mirror these thoughts.
If you believe that you are going to fail, you will unconsciously sabotage every opportunity to succeed. If you are afraid of meeting new people or having close relationships, you will do everything to avoid people and relationships, and then complain that you are lonely and nobody loves you.