My apologies. Somehow his extreme responses to emotional pain didn't make it into there when I was copying everything to the comment. For clarity, I'll do this point by point and re-write. [word count 299]

Daryl is often socially awkward and has difficulty letting people get close due to his childhood abuse (both physical and emotional) that extended long into his adulthood. Even those he thinks of as family and would die for, he keeps at a distance and doesn't share much of his past with. Particularly the parts that he thinks are shameful or would come across as 'weak'.

In add in addition to his self-esteem, he has some fairly extreme body-image issues due to the scars left from when his father took the belt to him. He dislikes taking his shirt off in the presence of others unless he's forced to or it's necessary for a doctor to have a look at him. This all plays into his desire to not to telegraph that he's struggling with coming to terms with his abuse and the recovery efforts involved. He'd rather no one recognize them, and if they do, they not bring it up or try to talk to him about it.

Daryl's emotional responses to pain and loss tend toward the extremes of either highly volatile anger (less often now, but still common enough) or episode where he mentally shuts down for anywhere from a few hours to a few days. He'll go through the motions and follow others, do what he needs to, but it'd largely a state of disassociation where he can try to ignore the pain, anger, and fear that's caused him to enter it. While he's like that, working things out, he becomes very subdued and generally unresponsive. This sometimes ends up with him being outright hostile to anyone that tries to approach him or confront him while he's in that state. Usually resulting in him yelling and being verbally abusive in an attempt to push them away.