You're in your final year of university. You're doing really well, you're getting stunningly good marks and lots of praise from your tutors. You've probably never been so happy in your life, you're using your incredible brain to think about really interesting, really hard problems. And you're starting to be aware of the frontiers of knowledge in your field, the stuff that isn't in textbooks yet, the stuff that people are right now actively trying to find out. Perhaps you did a summer project or a long finals project where you got a taste of actually doing some original research yourself, and it was mindblowingly awesome.