I'm a shy, reserved, and serious person who doesn't talk all that much. I'm a perfectionist of sorts, trying to get and maintain near perfect grades in my classes (I get a little upset if I get a mediocre grade, but I don't really show it.) The reason I said "of sorts", though, is because I'm also REALLY lazy. I loathe doing tedious work, which is most of the classwork I do anyway.
Regarding being "serious", I can "slip out" of that and act a little childish and carefree, but it only really happens when I'm alone or near my family. It can happen in public (ex: school), but it's usually when I'm really sleepy, which is usual since I stay up pretty late.
As a bonus, I get pretty attached to people I care for, so if you mess with them, I'll go up to your face and mess you up. So in short, I'm also REALLY loyal.