The Doctor looked frustrated and rolled his eyes. "How many times do I have to tell you, nobody is more important than you." A pause. "Well, maybe River, because she's my wife, but you? We have a friendship stretching further than most civilizations. Did I just ruin the moment, mentioning my wife?"
Missy's words reduced the Doctor to silent contemplation, and he was grateful when she submerged herself, giving him a moment to collect his thoughts before speaking again. "I'm fickle, and flighty, and self centered, given to brooding and distraction. I crave adventure, and freedom to travel among the stars. But among all these qualities, I never forget, and if you think that I have, then you're wrong. I miss my friend, too. And every time I went to a new planet, I think of our pact to see every star in the universe, and wonder what Koschei would think."