While they might not have been close at home and had really only talked when they were in the group or if they'd been paired as lab partners in class once upon a time, the compassion Lydia felt for him when she felt him lean into her hand and she saw that look in his eyes was very, very real. Someone like Isaac probably spent the better part of his life afraid of upsetting the people around him because when he'd upset his father, he'd been abused in response.
Everyone knew it and no one said anything and Lydia was just as guilty as Jackson had been, because she'd told herself it was none of her business when she'd climb into her car parked in front of Jackson's house and she'd hear the yelling only to note silently and piteously the next day at school that Isaac was sporting a shiner or a cast on his arm. She and her peers had collectively let Isaac Lahey suffer the shame, indignity, and pain of being abused for years and no one said a thing.
No wonder he was apprehensive of the idea of making a wrong decision; he'd been conditioned to be afraid to.
"You can," she encouraged. They all could. Everyone would take a different length of time to get there, she knew, and the fact that Stiles and Scott came from very shortly after Allison's death and seemed to have moved on without so much as a hiccup both here and at home while she and Isaac suffered in silence across the ocean and an entire continent from one another was proof of that. But eventually, they would all get there.
Lydia sucked in a quick breath as he began to unravel because she knew the feeling. She still had nightmares, too, and she hadn't even been there to see it. She'd seen Aiden's body and that was bad enough. Lydia took his wrists, guiding his hands back out of his hair when he made the stress response gesture. "Stop trying," she told him sagely and her eyes were swimming with tears again, but her expression was drawn with empathy and understanding. "Stop. Trying. The more you try to move on, the longer it's going to take," she explained. "You just have to let it happen in its own time, Isaac, and it will. It won't feel like this forever, it can't," she added and part of her was trying to reassure herself just as much as she was Isaac.
She let go of his wrists, took his hands and gave them an encouraging squeeze before letting go again entirely. "Stop trying to move on and just let it happen when it's time. It will. I can't imagine Allison ever wanting us to suffer and be miserable missing her forever or dwelling on it. She'd want us to move on and be happy, Isaac, you know that. You have to know that. Let yourself feel it. Let it hurt. Cry. Scream. Howl at the moon, if that's what you feel like doing when it hurts so much it makes you feel sick. You can't ever move on if you can't reach the acceptance stage of grief and you can't ever get to the acceptance stage if you don't let yourself mourn and go through the other stages. You have to feel it and you can't fight it. Let yourself feel it."