As the reel deal pointed out you should check out "The Secret". Its a pretty informative vid.
Otherwise, to quote Mystery "Any passionate relationship I have began passionately." Same with things. If I dont start out passionately on something then I rarely get passionate for it later while doing it. I kinda have the same thing where I start out strong and passionate and it kinda wears out for a while. Theres only three things in my life that I have never lost passion for (at least not yet) and thats psychology, living, and pick up. You do so many things and lead such an intriguing and varied life that it would be hard to focus on one thing but I also bet there are things in your life you are extremely passionate for like rap or kareoke. Lifes to short not to be passionate.