Draco's temper likely came as no surprise to the man who knew Draco since infancy. Really, for all Draco teased the Gryffindors, he well knew he was pretty crappy at holding his emotions in check. It wasn't that he didn't mean the things he said so much as he never intended to express his sentiments so cruelly. Perhaps he thought he couldn't hurt Severus. Hadn't he said as much to Lorcan? Still, it wasn't the emotional manipulation anyone implied. It took many days of soul searching and several chats with others for Draco to realize he might have pushed so hard because he wanted to see if he could hurt his old mentor.
Potter tried to help. Draco was grateful for it, but he was too close to the whole situation. Heck, even Colin was too close to it. In the end, Lorcan's fair approach helped Draco see some of Severus' viewpoint. Sirius also helped though Draco's estranged cousin couldn't know that; their chat helped Draco realize there really was no good reason to snip a family tree branch.
Severus was family. It was as if someone entered Draco's brain, shouting "Lumos!" on the top of their lungs. After that moment, Draco had scribbled the note apologizing for the misunderstanding about the potions payment, which eventually led to a conversation that didn't end in bitterness.
He simply couldn't help fretting over Severus. He cared about him. Even when he was bloody pissed, he was ready to attack anyone who harmed the man. It was just the way it was. Nevertheless, was he ready to really talk to his former Head of House? He felt like he was going to be sick.
He chose to prepare tea rather than change out of his sleepwear. When he heard the door, he took a deep breath and reminded himself he was just going to talk to Severus like he had countless times before. Resigned, he started for the door. He caught glimpse of his reflection in a mirror and grimaced. The lack of sleep showed in the bags under his eyes and he looked paler than usual. Gross.
He peeked through the peephole before unlocking the door. "Come on in."