Clearly you and Donna got along well for a reason. She taught me the value of just saving someone. We were in Pompeii the ay Vesuvius was to bury Herculanium and Pompeii for millennia. It was a fixed point in time, and turns out there were aliens preventing the volcano from erupting, so I had to cause the volcano to explode. Donna didn't let me do it alone. But I was prepared to leave as the city was about to be buried and Donna told me to just save someone. I didn't have to save everyone, but just someone.
I did. There was a family we'd befriended earlier in the day. I went back and saved them. The father in the family, he is the one who had this face I currently have. I chose it so I could remind myself that I'm the Doctor and that I save people.