at the beginning of Philosopher’s Stone, Hagrid talks about the bike he travelled on being given to him by Sirius, and in Prisoner of Azkaban (I think) he also says that he comforted Sirius when he was crying about James and Lily being dead at Godric’s Hollow.
So whatever you do, don’t think about Sirius arriving at Godric’s Hollow to visit his best friends and godson, all happy and cheerful.
Don’t think about him walking into the house and finding his best friend – his brother – laying dead in the hallway.
Don’t think about him then finding his best friend’s wife laying in front of the crib that his godson is sitting in.
Don’t think about Sirius grabbing ahold of Harry and clinging onto him, tears falling down his cheeks whilst Harry giggles, thinking it’s all a game.
Don’t think about Hagrid turning up at that exact moment, finding Sirius sobbing over his friends’ dead bodies.
Don’t think about Hagrid comforting poor Sirius as he clings onto the half giant and the small messy haired baby that resembles James so much.
Don’t think about Hagrid having to tell Sirius that he’s been sent to take his godson away from him.
Don’t think about Sirius arguing, fighting for his godson to stay with, though he knows it’s a long shot because everyone thinks he was the Potters’ secret keeper.
Don’t think about Sirius losing hope, and offering his bike to Hagrid to get Harry to a safer place, because he knows he won’t be using it for the unforeseeable future, and he knows that Harry will be safer wherever Dumbledore places him.
Don’t think about Sirius crying as he watches Hagrid take his godson away from Godric’s Hollow.