Kaidan hates his sleep shift. He takes all the extra hours he can aboard the new Alliance frigate to avoid the sleeper pods. Keeping busy doesn't help the numbness, it doesn't help him adjust to a ship that isn't the Normandy, but it's still better than the alternative.
When he closes his eyes... when he's alone in the dark... panic sets in. It's like the darkness sucks all the oxygen out of the pod and he knows this is how she must have felt in those last few minutes - alone and cold, suffocating in space. He remembers the Normandy evacuation – checking the survivors against the crew roster as soon as he touched down. He knew she'd want that information the second she landed. He remembers Joker, white faced and shaking as he climbed out of the escape pod alone. He'd known as soon as he saw his face. Even for her helmsman, losing the Normandy wasn't as painful as knowing that Shepard was gone. Gone trying to save his stubborn ass.
He can't forgive Joker. He can't forgive himself. He never should have left her. If he'd been there, if he'd ignored orders just once... he could have helped her. Together they would have been able to move Joker just that little bit faster. She would have made it into the pod, that beam never would have sent her spinning into nothingness... spaced... Commander Shepard dying all alone.
Kaidan had confronted death on Virmire. He'd looked at the bomb he was arming and he'd accepted the inevitable. But she'd come back for him. Against all odds she'd come back, she'd fought Saren, and she'd dragged his sorry ass to safety. In a lot of ways he has more in common with Joker than he's willing to admit.
In his darker moments he can't help blaming her. She should have evacuated the ship with him. She should have left Joker if he wasn't willing to leave the helm. But staying was so her, especially after Ashley. She wouldn't have left anyone alive on the dying Normandy. Not if she could help it. It was part of why he'd loved her. Why he still loved her. Always... always her.
So when it gets bad, he leaves the sleeping pods and finds somewhere to hide. Somewhere no one can see him when he can't help folding in on himself, curling around the pain and giving himself over to the grief.