Answer:
Integrity
Step-by-step explanation:
According to Erikson's Psychosocial Development when a person reaches an age that is above 60 is in the last stage of his/her life.
Here, Nathan is thinking about his life in a positive manner. He thinks his life was meaningful. This means that he will have his integrity. He does not think the actions that he took during his life were meaningless. If he were to think that his life was meaningless then he would fall into despair.