As students progress through the later years of their grade-school education, they gradually get to make some choices about the subjects they study. When they enter the post-secondary world the possible directions they see before them become far more numerous and bewildering. I generally encourage them to keep their options open by pouring their effort into the most challenging courses so that they keep their options open.
This partly comes from having worked with older students who took the easiest courses they could find and then, after a few years of dismal employment prospects, sought me out help them get started with the math and physics they needed for science or engineering degrees. After their time with me, they move on to more advanced courses where they have to make more choices. Once they graduate from university, they will have to make decisions about finding a suitable balance between becoming specialists or generalists.
This article by self-study expert Scott H. Young, one of my favourite bloggers, offers some excellent advice on exactly these issues.