Explore! I cannot stress this enough in order for you to stay motivated and truly dig deeper into your interests on a personal and professional level.
Don't expect to experience a burst of realization of passion when you haven't bothered to actively participate in things that interest you. Try to identify the areas that you find yourself most creative, determined, and happy.
Go out and try new things, whether it is hiking or joining a club that you thought you didn't “fit” in! Even minimal interests could lead you towards something bigger, just follow it.
Most importantly, remember that it doesn't have to stem in school. In fact, try to join activities out of school to help you meet new people and take a break from the school atmosphere. Even if it is academic, it doesn't have to be from school. Just be open and have the initiative to go out and experience new things!
Also keep in mind that not everything you do will be something you will continue forever. So, don't assume that you MUST continue everything you start. Just find your areas of interest and have fun!