The Doctor didn't want to leave. He wanted to know what that thing was, he wanted to know what very nearly happened to him. He wanted to sort this out now.

But he jumped in without a thought. It nearly cost him a regeneration (or had it given to him, whichever the case was). And Jack...He'd hurt Jack, not just with his actions. The Doctor was impossible at times, but this was far worse. He wasn't sure what he wanted, and he thrust the blame of that onto his companion.

The least he could do was relent.

"All right," he said. "Let's go."