Tote the Weary Load
He should have tried out for the Gryffindor Quidditch team. Whenever he flew with James during the summer holidays, he was always able to keep up. He might have made an excellent Beater. He should not have teased Regulus -- anyway, what had his brother done? He should have not cheated on his final exams in Fourth Year. On the other hand, it wasn't his fault that Miranda Baron made it her papers far too available for his eyes.
Sirius Black has made his share of mistakes. These mistakes are largely trivial, forgotten in the instant they are regretted.
He should have been born a different person. One, after all, cannot be a disappointment to one's family if one was never part of that family in the first place. He should have run away earlier. What was the point of enduring yet more days, weeks, and months of shrieking admonition from dearest mother? He should have worked a little harder for the Order. Was that even possible?
Sirius Black has made his share of mistakes. These mistakes weigh like cold air upon his thoughts, but as he surveys the haphazard beams of wood, the stench of smashed pumpkins, and the cracked sign that once read "GODRIC'S HOLLOW," he knows this one will be the heaviest one of them all.