I know, this is all not part of any case or his personal storyline, but I wanted to highlight some things I think about the character, this seemed to be a good way to me.
(Zack, training to 'put his heart in a box')
Just do how Dr. Brennan said, put your heart into a box.
He lays there, knees pulled up to his chest. The blanket even up to his eyes.
"I will have back full control. The Doctor said, since I can feel, it would be most likely to get back control, too. 80%. But can I still trust any calculation? It's different. She said you can't calculate humans. I am a human and the Doctor is, too. But that didn't she mean. She talked about feelings."
It almost never works at night. He can put his heart in a box at work. He even manages to do so, when they're at the diner. They make fun about him, but most times, it's okay. He could do it, when there was this young boy, laying on the cold grey table. Dead. Decomposed. Probably raped. Murdered. He cried that night. He almost never cries. He once cried, when this one bully in high school hit him in the face. He lost a tooth. He was 14. The other one was 17 and of course, someone from the football team. That was the last time, someone saw him shedding a tear.
He does like he always does, when there is nothing else to do. He talks to god. He doesn't believe, that someone is listening. He doesn't believe there is a god. But his mother once made him talk to god, and he thought it helped. It was one of these things he could hardly understand.
"Please, I don't want to trade my hand for love. I know, there is probably no way these two things could influence each other, but I feel like it. I understand, some things are not made for being calculated, but this is. You don't have to prove anything more to me..."
It doesn't help. Now he wonders, if he is going crazy. How should talking to 'god' help, if you don't even believe in god? He turns around. 00:01. He has no better word for how he feels, than lost. He thought, it would be nice, if his mother could be there. Comforting him. But that's something of the past. Long, long time ago. Then his thoughts flip, there is someone else, in his apartment, who could do that.
A new wave of anxiety hits him. He doesn't know how to do that. He doesn't know, if that's weird. He never knows. But he feels bad. He can't remember the last time his body reacted that way to something like fear. He knows the matching word. Panic. Panic over the possibility to lose his hand, too lose his job, his friends. Losing his job, would be like losing his life.
"I can calculate this. I can calculate her reaction. She is always nice to me. She agreed to make it officially you date... I asked a lot of questions, she never said anything, there must have been at least 2-3 really weird questions. She's good with feelings, she will understand." That's it. He finds his courage and gets up.