It seems that “metanoia” really means a change of mind with respect to action. So the mental aspects of getting your life turned around would be metanoia on a grand scale. Sounds pretty close to “conversion,” but I like the Greek word anyway.
But what’s the need of conversion? Why want to be transformed into something different from what you are already? Doesn’t the aspiration to do so show a sort of sickness, or at least an antisocial rejection of life and humanity as they are? Why not be tolerant, open yourself to the world, and go with the flow, appreciating what there is without being so critical?
The answer, I think, is that life and the world are themselves incomplete and in conflict. They point beyond themselves, and can’t be understood simply on their own terms, as a self-enclosed system of things. Accepting life simply as we experience it is a modern fantasy. Otherwise, why would men have always recognized the gods? Why was Nietzsche, who rejected the transcendent, always on the attack? Why did the Buddhists and Taoists drop out of society as well as out of established rituals and conceptions of deity?
We attain stability and the self-realization that suits us only through orientation toward something unseen that lies beyond us, and the most basic question for all of us is what that unseen thing is and how we relate to it. The need for conversion—for reorientation toward something beyond us—is not a sign of particular weakness, but a recognition of our essential position. Religion is not an add-on, it’s essential to our humanity.