"as long as you are pretty rational about what "right" means"

That's the deal. What I'm talking about when I use that phrase is that so often we're so convinced we're "right" about matters that are personal preference, or are actually trivial that we get blinded and insist on "getting our way". That's rarely a path toward happiness. As I get older I'm more tempted to let the other guy get away with it. Lifes too short to get upset about the driver who cut you off in traffic so he could be "first".

For that matter - who cares if I think there is a God or not? Does it really matter what anyone thinks? What I think doesn't bother anyone. Now if I take some action resulting from those thoughts that harms you - that's something different alltogether.