If Sirius had a knut for every time someone said "Watch your temper, young man, it'll get you into a lot of trouble one day," he would be one rich convict. However many times he heard the idle threat, he never heeded it. If he could've imagined just how much trouble he would get himself into by venturing outside of Grimmauld Place when he was supposed to be undercover, would he have done anything different? Nah, probably not. Not for all the éclairs in Tesco.