To dream anything that you want to dream. That's the beauty of the human mind. To do anything that you want to do. That is the strength of the human will. To trust yourself to test your limits. That is the courage to succeed.
Dreams are a way for your subconscious to release any pent up worries or frustrations, and for you to visualize your goals and objectives in life. Everyone dreams, even if these subconscious movies are not remembered when you wake up. Dreams are different from nightmares because dreams are typically pleasant while nightmares are terrifying or disturbing in some way.