Disclaimer: J.K's inventions, my random ramblings about them :)

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The first time was his first week at Hogwarts.

He and James wanted to do something big, to tell everyone that a new generation of pranksters had arrived. They decided to bewitch a rubber ball to follow Professor McGonagall about everywhere she went, bouncing off her back with every step she took.

And even though it was awesome, even though it put them on the map as the Marauders…

The five minutes of fun just wasn't worth the month of detention they got when she caught them.

* * *

The second time was a stupid thing, and he rarely thought of it again, but at the time, it had seemed huge.

He was in Second Year, and James had asked him to come along to Quidditch trials with him. Sirius had laughed, joking that he wouldn't want to steal focus, that he was too good for the school team, that it would cut into valuable pranking time…In truth, he was scared. He, Sirius Black, was actually scared. Scared of not being good enough. Scared of looking stupid. Scared to try.

And so James had gone alone, and was instantly recognised for his talent. He was awarded the position of Chaser, and Sirius had congratulated him, attending his first game along with Moony and Wormtail (and every game after that). He had cheered wildly along with every other Gryffindor when his best friend scored his first goal.

But deep down, deep inside his heart, he had felt a pang of regret – if he had been brave enough to try he could have been up there too, he could have helped James score, they could have congratulated each other…if only he had tried.

* * *

The third time was more serious, and the regret he felt then didn't leave Sirius for a long time.

He had thought he was clever and amusing, telling Snape how to get into the Whomping Willow. Just a bit of fun, he had said, just a prank. James, thankfully, had stopped it before it had gone too far, and Remus had seemed understanding, had offered forgiveness.

But deep down inside him, Sirius felt it – not for nearly killing Snivelly (he deserved it), but for what he had done to his friends.

He had dented their faith in him, their trust in him. And though they moved on, and accepted it, and forgave him, Sirius knew that they wouldn't – couldn't – forget. They could never trust him in quite the same way again.

And he regretted that for the rest of his life.

* * *

His fourth regret came as he knelt in the rubble on the corner of Godric's Hollow, sobbing over the lifeless body his best friend.

He mourned for James and Lily, and their lost lives; but he mourned for others too.

His godson Harry: how could he grow up with no-one in this cruel, cold world? How would he cope, never knowing his parents, never knowing their love?

He mourned for the families of Lily and James too: how would they deal with the loss of their children? How would they survive, knowing they had been murdered in cold blood?

And Sirius mourned for himself: for the loss of the only family he had ever known, the only people he had ever truly cared about.

So as he knelt there, a battered, broken man, Sirius regretted with all his heart ever encouraging James to switch his secret keeper; for ever trying to outsmart Voldemort.

Because he knew that if he hadn't done those things, he would have nothing to mourn.

* * *

But Sirius' final regret was his biggest one, and it came not during his life, but after it ended.

As he watched over his Godson from above, seeing him risk everything and everyone he loved for the good of wizardkind, Sirius regretted not telling Harry about the regrets of his life, and not warning him what a powerful, life-changing emotion it could be.

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Author's Note: So what's the verdict? This is the first kinda angsty thing I've done, so I'd really appreciate some feedback. Go on, push the button :)