When they kissed, the Doctor could hear the drums, and the Master felt the guilt and need for forgiveness lingering in the Doctor's hearts.

When they lay in bed together like lovers, the Doctor could feel the Master's insanity and madness rising within him, and the Master got to watch Gallifrey burn.

They both knew that one day their relationship would end. And every day they both prayed that it wouldn't be today. But they also knew that praying wouldn't always be enough. One day the Doctor may give into the drums, and one day the Master might need to grant the Doctor the forgiveness he was seeking.