Salem doesn't get a second of sleep that night. Seriously. He doesn't fall asleep at all. He can't, not with all that's on his mind.
Salem has spent every day since their breakup believing Atlas hated him. Well, maybe not hate, but Atlas really did do a fantastic job of making Salem feel like shit that day—well, for months actually, if you count the fallout. He made it the worst possible experience, pointing out every flaw in their relationship, every flaw in Salem.
Of course, now Salem knows why. Atlas wanted Salem to hate him.
Atlas knows him very well. He knew the things to say to absolutely destroy Salem. To break Salem's heart and cause him the maximum amount of emotional pain. However, unfortunately for Atlas, he strongly underestimated how much Salem loves him.
