Luke:
Everyone knew it including Luke himself, but even because of that and constantly thinking about it all the time, he didn't change what he was doing. The bathroom would always be such a mess when leaving it after a shower and even if he had decided to place towels before walking in, they were still soaking and there was water everywhere. He always thought that he needed to clean it up but he was using so much time on just walking around with a towel around his hip and doing absolutely nothing. Eventually he would get back to earth the second you would step into the bathroom with the biggest yell of his full name that he had ever heard in his life.
Calum:
He knew the smoking was bad, he knew that you preferred him without the nicotine in his body but he still couldn't stop. He was aware that it was disgusting and only ruining his voice but he also believed that it all had something to do with mind control. The second that he knew he would be ready to stop, if something life changing would come up, he knew he would be strong enough to do it. But with stress, constantly travelling and stuff coming and going he didn't have the strength right now. It was his small pause every now and then and with you companying him on the balcony he felt the best with a cigarette between his fingers and your hand in his even just for a short minute.
Michael:
It had been constantly spoken in the fandom and even after three years the video was posted he was still doing it. It wasn't something he thought about during the action, but you would always, always, stare at him with a half disgusted half amused smile. Especially because it wasn't until he had eaten half of the bowl with chips that he made the face of 'did I do it again' and shaking his head by himself. He was a clean person, always wanting his hands to be hygienically he had to sprinkle off the small crumbles from chips. He knew that you thought it was somehow disgusting but he couldn't stop doing it. It was a habit that had stayed with him for years and it didn't seem to stop now or then.
Ashton:
You never understood where all the hair ties went because you literally felt like you bought a new package every time you went down to the grocery shop. You would complain, curse and walk around in frustration but little did you know that Ashton was the one hatching them all the time. He always told himself that he would put them back after use but it was the magical thing with the hair ties. They always seemed to disappear without him knowing where in the world he put them because to him they were always resting on the dresser. And even if you had cursed over him stealing them and buying new he would do just exactly the same, using one and forgetting where he put it.