Thought
It is generally considered that, "As you act, you become," and the Bible said, "As a man thinketh, in his heart he becomes." that explains why most happy people are successful. This does not always infer material success. The process of being successful does not know time, our mind does. Hence to succeed is a process within us wanting to manifest what we have put into our mental imagination. So what are you putting in there? Remember, the better your thoughts, the greater your success. Focus on changing the way you think, the many things will change.