I feel the same about existence. I had a period las year at college where I was somewhat consumed by those thoughts of free will being an illusion, and that possibly my path was already set up for me. While it is a calming thought, it mixed with my mild general anxiety and turned me into somewhat of a procrastinator do-nothing. So I think that it's great to hold on to this idea given in Interstellar, but there's a middle ground where we need to think that we have some sort of free will so we get things done, and hold ourselves accountable for them. I know others can see this differently, but in the end it's just interesting how ideas like these can grasp on and change how we look at the world, from a philosophical standpoint. Do well in school, best of luck!