You can develop the right mental attitude when you realize that nothing external can upset you or hurt you without your mental consent. You are the only thinker in your world; consequently, nothing can move you to anger, grief, or sorrow without your mental consent. The suggestions that come to you from the outside have no power whatsoever, except that you permit them to move you in your thought negatively. Realize that you are master of your thought-world. Emotions follow thought; hence, you are supreme in your own orbit. Do you permit others to influence you? Do you allow the headlines in the newspapers, gossip, or other criticism of others to upset you or bring about mental depression? If you do, you must admit that you are the cause of your own mood; you created your emotional reaction. Your attitude is wrong.
~ Joseph Murphy, Believe in Yourself