"Since I am in the midst of my travels...I must bid you farewell. Shouldn't you be returning home as well? Whenever there is a meeting, a parting is sure to follow. However, that parting need not last forever... Whether a parting be forever or merely for a short time...that is up to you. With that, please excuse me..."
—The Happy Mask Salesman from The Legend of Zelda: Majora's Mask
"I have to go now. My planet needs me."
The narrative restoration always comes at a price. The Doctor can get out of anything, but the flip side is that he is always going to be alone. The Doctor's fundamental move - the first trick we ever saw him do - was to fall out of the world. To escape. But when you escape, you are, in the end, alone.