An emotional scene from Heaven Sent (2015).
After finding the final challenge in Room 12, the Twelfth Doctor (Peter Capaldi) retreats to his TARDIS/mind palace. He grieves over losing Clara Oswald (Jenna Coleman) as he contemplates throwing in the towel.
For a brief moment, his long-dead companion encourages him to proceed with the impossible task.
Back in Room 12, he then punches his way through a 20-ft wall harder than diamonds, before the ghastly Veil reaches him.