Doctor Who Series 10: 11 Easter Eggs & References You Might've Missed In 'Thin Ice'
4. The Doctor Has Moved On
After a little urchin boy dies, Bill reprimands the Doctor for how quickly he gets over the death. When he admits that he has seen a lot of death, she asks him if he remembers how many people he has seen die and also how many he has killed himself. The Doctor cannot answer and says that he has "moved on."
A similar scene occurs in 50th anniversary special The Day Of The Doctor. The Tenth Doctor berates the Eleventh Doctor for not remembering how many children were on Gallifrey the day that he was forced to destroy the planet to end the Time War. Number Eleven admits to himself that he has "moved on."