Habit rules us all.  

You have formed, perhaps, the habit of thinking of yourself as a common person, as one of a limited ability, or as being more or less of a failure. Whatever you habitually think yourself to be, that you are. You must form, now, a greater and better habit; you must form a conception of yourself as a being of limitless power, and habitually think that you are that being. It is the habitual, not the periodical thought that decides your destiny. It will avail you nothing to sit apart for a few moments several times a day to affirm that you are great, if during all the balance of the day, while you are about your regular vocation, you think of yourself as not great. No amount of praying or affirmation will make you great if you still habitually regard yourself as being small.