The Doctor felt the silence echoing in his own head and for just a half second he shared the Master's... joy. Then he fell back into his chair and his own brain. It wasn't controlled. He didn't leave, he fell. Everything gave at once, with the lack of resistance.
His hands fell away from the Master, and he just slumped. Eyes wide open, completely unfocused. He wasn't breathing hard, he wasn't shaking or twitching. He was just utterly limp.