Steve didn't understand. He couldn't. Somewhere underneath it all, Bucky didn't want him to have to. He didn't want Steve to know what it felt like to want to not be in yourself anymore, or to look in mirrors and want to break them because the alternative was clawing at his face or yanking off the arm they hadn't asked him if he wanted, just put on him. Take something away, put something shining and inhuman in its place - that's what they wanted from him.
You couldn't be a thing if someone was there who wanted to help you be a person. Steve wanted to help and Bucky didn't want to be helped. He wanted to be absent, and he wanted Steve to be safe. Those were the only things he could bring himself to want.
Bucky made a sound, slight and frustrated, a wordless little grunt from someone who was rapidly running out of words and didn't want to find them anymore. "I don't need that. I need you to be away," he repeated. His brain wouldn't fight its way back through the mire to try to find another way to explain or deflect that might work better. It just hung on to the one path it had found. "Just go, Steve."