Castiel heard the fear in the other's voice, and saw the heart of it in his eyes. He stepped forward closer, too close for most observers of personal space, and placed his hands on either side of James' head, concentrating. He hadn't healed too many people since losing his powers, but as he focused his magic on healing he found it as natural as it had once been, as easy to control.
He concentrated the power on the mind. There was no way to piece a soul back together; the owner had to do that for himself if there would be any permanency to the procedure. But Castiel could see the cracks in his psyche, the injuries that were keeping him from piecing himself back together. He didn't erase any memories, but he eased them, pushing back the most terrifying and painful and strengthening the positive feelings and thoughts. Deleting the pain would have been easier, but carried the risk of fundamentally altering the man, and Castiel had grown to appreciate the opportunity to overcome one's own pain, instead of burying it to be potentially re-exposed later.
When he finished his work he flooded the rest of James with the warm healing energy, taking care of his physical form before lowering his hands and stepping back. "I could be more drastic, but the best way to ensure it lasts is for you to heal on your own as much as you can," he said, studying the soldier carefully.