Grimmauld Palace exuded this type of aura that seeped out from the cracks in the walls and deep from the grain of the rotten wood it was made out of. Years of dark magic swelled within its walls and hung in the rooms like an acrid smoke. Overall it wasn't and isn't a very pleasant place to live, even for those who have been exposed to dark magic for years.
Memories and events are powerful things, they rub off onto the place around them and stick around for decades or longer. When you live in a place like Grimmauld Palace and know what's happened in its walls, you will always see the ghosts of memories dancing in the corners of your eyes. You will see bloodstains that have long since been spelled away, and hear voices or noises that have ceased to exist.
When you're Sirius Black, the walls never seem to stop making sounds, you still see the flashing lights of spells exploding behind your eyes when you walk into the living room and hear your parents voices in the back of your mind.
It's a very lonely existence, seeing ghosts no one else can see, remembering things other people haven't known or have since long forgotten.
The looks you get from the other members of the Order make you want to crawl away into a corner where they can't see you. You don't want to see their expressions when they find out you have those bouts of fits when you walk into the wrong room or someone says the wrong thing.
Oh how you hate those fits. You had them when you were younger too, when your parents were still alive and you lived back in Grimmauld. Your chest would tighten up and it felt like your skin was buzzing and it felt like your head was about to explode. You couldn't breath and it felt like your heart was expanding and collapsing at the same time.
Remus once told you something about panic attacks, but that's silly, you couldn't be having those. Could you?
Sometimes it would get so hard to breath, you would see black in your vision, and then you would wake up on the floor shaking and it'd be night time. Once you woke up in your bed and the curtains were drawn with the room silent, and for once you could think.
James once told you that it wasn't right what was happening to you, but Regulus had them too, so maybe James was wrong. There was nothing wrong with you right?
When James and Lily died they were all you had, all you had in your prison cell, the blackness, the buzzing of your skin, and the choking feeling inside your throat. Soon that died away to listening to Bellatrix scream at you, and watching the walls until the sun went down and you were staring into the darkness.
You still did that sometimes, stare at walls. You'd do it when you're in your mothers room and were grooming Buckbeak. Then you'd just lay down on Buckbeak and not move, because your limbs felt to heavy to get up, and it took you five tries to get up. And when you did, you cried.
Remus used to hold you when you were in school so you wouldn't pass out when you started seeing the black. But that was back then, before James and Lily died. Now Remus skirted around you like you actually did kill Lily and James. And maybe you did.
Sometimes you didn't know what to think. It just hurts to think, so you don't. And you go to sleep. Or you sit in the kitchen and argue with Molly to distract yourself.
But that doesn't matter, you're fine right? Right?