"Because of stupid, stubborn pride. And because we're far more alike than either of us wants to admit." Missy gently wiped a tear away from his cheek and smiled sadly. "If this isn't permanent and I change back... don't let the Master continue down the same path. You've seen that I could change with time and effort. That means he can too, Doctor. Being brought here is his chance to see the stars instead of burning them. And if I am here to stay, then don't give up on me either."