I think... I feel good about it.
Who: Marvin the Paranoid Android
Source: So Long, and Thanks for All the Fish
Notes: Character, a robot who through several time-travel mishaps was now "37 times the age of the universe", at last shuts down after seeing God's Final Message to his Creation: "WE APOLOGISE FOR THE INCONVENIENCE". Character had been a drastic pessimist, making this final quote his one even somewhat happy moment.