Castiel felt powerless. He had shattered his good work toward proving his self-sufficiency in an instant, and now he felt like he was underwater. He couldn't even hold a conversation. They were pulling into the park where he had spent his first few nights here. Dean probably didn't know that, but Castiel felt irrationally worried that Dean had taken him here for some sort of lesson, to make him look at his sorry life. He wondered if Dean's gentle tone was a way to lull him into some peace before putting him out of his misery. He didn't believe Dean was capable of that, but he pictured it with hope anyway.
In the meantime, the sounds of birdsong and feel of the gentle breeze on his face were comforting. He still couldn't get over how different it sounded to him now. How these sounds that used to carry mere information could tug at his heartstrings now.
"I'm sorry," Castiel ground out from his throat. As fast as life drained back into his limp body, it manifested as tension. He couldn't move his locked limbs, but he could at least try to smooth things over with Dean.
"Cas, what are you sorry for?" Cas paused; the question didn't compute. His brain was still sluggish. Dean grabbed Castiel's hand as if he'd done it a thousand times. It was warm, and Dean's gaze on his face was warm. Cas still couldn't look at him.
"You don't have anything to be sorry for, you hear me? This is on me." Cas couldn't. He just couldn't put up with this again. He was suddenly near a tree, walking rapidly. Maybe he could make do without wings after all.
"Cas!" He didn't stop. "Cas, what the hell, man, we need to talk!"
He spun on his heels to face Dean--now practically on top of him--to give him a piece of his mind, his frustrations, his hopelessness. He knew everything Dean would say. He didn't need to hear it. He didn't need to hear some lecture about what was appropriate. He didn't need to hear how clueless Dean thought he was about human customs and relationships. He didn't need to hear Dean blame himself as always, to assume some patronizing role and teach Cas how to behave. Castiel was eons older than Dean. If he was defective, it was because of this stupid situation, and he'd brought this situation on himself. He didn't want it fixed, he just wanted to die before he endured any more humiliation.
But nothing came from his mouth. All the building energy bubbling from deep inside him found his throat and mouth locked up, was shunted to his pounding head, pouring out his eyes in shameful rivulets. He shut his eyes tight but couldn't stop it. The harder he tried, the more light-headed he felt. Suddenly Dean's hands were grasping his upper arms.
"Breathe, Cas, you gotta breathe." He tried to comply, but his body was shaking and the breath was only making it to the back of his mouth before it huffed right back out of him. "Cas!"
As the edges of his vision got hazy and his confusion mounted, he suddenly found himself buried in Dean's chest, breathing in that comforting scent in the side of Dean's neck. Dean's bear-like grip around his torso was giving his lungs some context to ground themselves in, and the soft scratching of Dean's nails through the back of his hair gave his racing thoughts a place to land. "I'm so sorry," Cas mumbled, losing himself in the sensations and not caring one bit what happened next.