Robert Collier, in Secret of the Ages, said that you can do anything you want to do, be anything you want to be or have anything you want to have. You have to know what you want, and you have to attend to your subconscious, your ambition, the Genie-of-your-mind as Robert Collier calls him. He points out that many people had Ambition as their driver when they were young, but when they became men, "He gave up on most of us as being poor, hopeless things."
First, you need desire. What is it that you dream of? What is it that you would work for day and night, because you may be called on to work that hard at first? Is there someone or something you would risk your life for? Make a picture of the successful accomplishment, and feel the feelings of having gotten it. Picture what you would do if you achieved your dream. Picture it as if you have it now.
Then, desire is not enough. As Robert Collier says, there must be BELIEF, too. “What things so ever ye desire, when ye pray, believe that ye receive them and ye shall have them.” You must realize God’s ability to give you every good thing. You must believe in his readiness to do it.