Firstly to find your calling you need to know what you like to do. But by the time you graduate, schooling has eroded your natural sense for detecting things which genuinely excite you. Think about it - You have just spent the last 17 or so years in a formal schooling environment non-stop. Since young an authority figure has always been telling you what to read, study, and write and then monitoring all that you have done. Most of the time you are answering questions rather than asking them.
Formal schooling has a tendency to promote breadth and not depth. How many times have you given up your interest of reading further into a module you enjoy due to the workload of the other modules? How many times have you not pursued your passion, in fear of not making the grades for the rest of the modules?
Do you remember the times when your parents reviewed your report cards, telling you to improve on the Cs but never telling you to focus on the subjects you got As for? In school you're taught to pursue a broad area of studies and not thought to specialise. But in the real world only those who can discover and build upon a couple of core natural strengths and interests are rewarded.
Therefore to conclude, formal schooling dulls one's exploration of natural interests. So ask yourself what you naturally enjoy and then pursue it vigorously. This so called unusual behaviour may not go down too well with the people around you. Unfortunately, asking yourself this very question is the key to a rewarding real-world career! So you decide - be pretty good at lots of things or be extraordinarily good at one thing.