The Mentalist, Season 2

Lisbon:
You're leaving?

Jane:
Well, frankly if I can't use this job to seek some kind of personal revenge then, uh, there's not a whole lot here for me. I don't make anything better. I can't bring dead people back to life. What good do we do? We drive around California visiting unhappy people.

Grace:
We're fighting evil and injustice.

Jane:
And how's that going? Any progress lately?

Cho:
We put bad guys away where they can't hurt people. That's good enough.

Jane:
Nah. I was doing more good as a psychic. I was giving people hope at least. False hope, but hope anyway.

Lisbon:
You're right. Best you leave. That way you can go back to being a full-time fraud and we can continue our useless jobs in peace.