The way education is set up atm you *need* to know you're going into medicine or CS or whatever early because you don't start in college, you start in high school. If you have to retake a class or mess up your GPA one semester or don't take the right classes you might not get accepted where you need to go. That was never my path but I remember my buddies in HS being so stressed about it genuinely convinced that one poor semester would alter the course of their lives and I'm not sure they were wrong.