Thats the thing...you do what makes others happy. That is why your passion does not last, or maybe it never trully existed. Passion comes from doing something 'YOU’ love doing, and it does not feel like work, but rather like a hobby. Its normal to lack interest when it comes to others choices of interest, after all we all were made unique, with unique aspirations and pasions. You just to dig a little deeper at finding, what it is you enjoy and try it out, try out a bunch of things and stick to one that makes you want to do it everyday as best you can.