Most of the time Jackson is the easiest person to be with. He has a sunny unproblematic personality, forgiving and caring. He's the kindest person Jaebum knows, which is why it's so heartbreaking to see him suffer.
Because sometimes, sometimes Jackson is the hardest person to be with. Sometimes, on bad days, he shuts everyone out, even Jaebum. Sometimes he just lies in his bed and thinks terrible things about himself, not listening to anyone. It sounds horrible, Jaebum knows, but it's easier if Jackson cries. Because when he cries he doesn’t push Jaebum away, and Jaebum can lie down with him and hug him as hard as he can.
He says: you are beautiful. He says: you are talented. He says everything that comes to mind as long as Jackson allows him to say it. (Sometimes he doesn't, sometimes it just makes him cry harder, so Jaebum tells him how much he loves him over and over until his throat hurts and, thankfully, Jackson doesn't fight him on that).
He feels helpless all the time. Turns out being helplessly in love has a different meaning than what he has always thought.