I actually looked at this yesterday during a short break I gave myself while preparing a presentation. I liked it of course but couldn't really get the relieved feeling because I was personally still extremely stressed and busy. I worked till 12 and gave my presentation early this morning, still had to endure a whole day of the course and now I'm finally home. Now looking at it I can take in the message a lot better. I always loved the way you're drawing Ron because he's so damn handsome with his perfect hair, tallish figure and his features are just what I imagined them like. Hermione's hair in this one is just fantastic and their pose together looks really nice. In my opinion you're one of the few artists managing to draw a realistic Harry but here he is even better than normally. Aaand to sum my comment up I think Ginny is the most striking thing about it because she looks sooo much like a top model with her endless hair and wonderful eyes. I always thought she was pretty because in the books she gets all the boys ;D and I'm pretty disappointed with the film Ginny so once again I like your interpretation a lot better.
Of course all these things are not only concerning this particular drawing but as it is just wonderful I thought I'd tell you now. Keep up the great work and don't worry too much about your exams. In the end all will be well.