After a lifetime's worth of adventures--some by herself, some with Ashildr, and a few random ones with others who had also known the Doctor--she decided it was finally time to face Death. After all of her experiences across time and space, Clara was tired and truly felt her age though her appearance fooled all who met her; she didn't think she was as old as the Doctor himself but certainly more than the average human.

As her soul returned heavily and reluctantly to her real body, she looked up for the last time into the eyes of the Doctor and wished she could tell him everything was all right and that the Impossible Girl had already seen all the universe had to offer but all she could do was silently say to him, "Run, you clever boy and remember me".