In the Victory of the Daleks:

They knew you would choose the Earth. Because you're weak. You can't even defeat your greatest enemy if your precious humans are threatened. They were there! You could have defeated them! But no, the humans were more important, and now there the Daleks are, wandering through space, destroying more and more civilizations because you couldn't give the Earth up. You couldn't give yourself up. You never could. You destroyed your people, but what do you do? You survive. You hit the button and leave. You always do. You always have.

It wasn't my choice! It never was! I always have the choice of millions versus the few, the pros versus the cons. And I always choose the humans because they matter. They have emotions. They have feelings. And there will never be a time where those humans will not amount to anything. They're all I have. So I have to save them because I couldn't save my own people. It is my debt to be paid. It is my job to be done, and I will do it to my fullest potential.

Bold- the Doctor's Darker Side

Normal- the Doctor's Helpful Side