Sirius Black likes to present himself as a laid back guy. Sure, there are some aspects of his life that induce anxiety, but no one would associate the young Gryffindor with the word scared. When his friends ask how was his summer, he brushes it off; when he sees his brother befriending future dark wizards, he tells James that he is his brother, and he is his home and not some slimy bigot. On the days leading up to a full moon, Sirius eagerly plans where they'll take Moony next, and making impatient comments about how bored he is. He ignores the little voice in his head, that sounds suspiciously like his mother mentioning everything that can go wrong, especially when you get involved with half breeds. He blocks her out and forgets and has the time of his life during those nights. It's nice living that way, for the most part.
He has a solid group of friends, a brother in every sense but blood, pranks and adventures and even some popularity. And until his sixth year, everything was going smoothly, and maybe dare I say it - ideal. However, the circumstances life throws at you aren't always ideal, and can be sometimes downright nasty. And if Sirius thought he had it bad, soon he will be able to appreciate the concept of hell a little more.