John constantly assuring Katie that he's going to get her home. As well as his relationship with his daughter.
Episode 9 of Vengeance. Throughout the series, Stonebridge has been agonising over his pursuit of Craig Hanson, the man who killed his wife, and he's now convinced that it was a mistake to come back to 20. Dalton sits with him and tells him:
"I said that I would take you based on your psychological evaluation. But I have never opened your file or read it. I brought you back because you make all of us better soldiers."