I'm well aware that rationality or rational thinking tends to be associated with atheism or any school of thought that negates a concept that lacks empirical evidence. But, what I learned is that rationality isn't dissonant with spirituality, in fact, it morally compels a person to go beyond logical fallacies or cognitive biases to explain why he/ she subscribes to a particular system of belief. It prevents complacency.
What I like about rationality is that it allows the mastery of one's self--of one's emotions. It prevents clouded thinking and irreversible, damaging behavior when in the middle of a confrontation. I especially find it useful, as suggested by Julia Galef, to imagine that your personal opinion is a physical construct that you put in a box and place beside you while your "opponent" literally "attacks" that box with his/ her points of argument. It removes the notion that the attack is on you; "Argumentation as collaboration rather than combat." Whereby after the argument, you get to take home your opponent's weapons.
Apart from argumentation, the practice of rational thinking helped me to sleep better. I don't over-analyze other people's behavior and I've become less anxious about how other people treat me. That's the thing about all of us; we're all so occupied with ourselves. We think that everything that offends us is a deliberate provocation, whereas it's also purely possible that people aren't even thinking about us at all.
Rationality, a change in perspective. Hear, hear.