This is hard for her, too.

I'm well aware. It absolutely is.

The strategies we're discussing on this thread, though interesting and maybe useful, are probably not things you want to use with your wife...

I agree, and tend to abide by that advice. I think when I provide rantish outbursts trying to justify myself, it's usually because:

• The discussion of our kids comes up and she thinks she has more of a right to raise them to believe Catholicism, citing as her primary reason that it's really important to her. That's quite challenging and usually leads me to want to stand up for myself regarding the amount of work and research I've put into this and how I think that counts as a valid reason that I have an equal say as well.
• When I feel proselytized. She brings up leading topics, in my opinion. She came back from a retreat and told the valiant story of a man who doubted but said to himself, "Well, if there's a heaven, even though I doubt, I'm going to spend my entire life trying to believe anyway so that I can go." Given the pertinence to my own story and the fact that she shared nothing else about the retreat other than that, my bet was on her trying to defend my stance and why that logic isn't sound (which belief is the right one to get into heaven?). (She verified later that it was, in fact, a conversion-directed comment.)
• When I feel challenged about my process, like if she poo-poo's what I've read, chalks it all up to bias, or something similar.

I guess I could go on a little bit, but just wanted to cite some of the items that have a tendency to draw out the "defensive me."

Other than that, I can say with near certainty that our best times have always correlated with our longer-ish periods of just not talking about religion/my quest at all.

You're a new person, so start a new courtship, getting to know each other again.

I had this thought several months ago, actually. I realized that I tend to talk pretty openly about anything and everything -- what I read, things I find interesting, work, etc., but that she doesn't always do this and that I missed "knowing her."

We also began marriage counseling and I stated as one of my goals at our first session that I think finding new "common ground" will be important. We need something to fill the void left by our shared bond via religion.

Don't try to change her, but change yourself.

I (perhaps obviously) agree with the second admonition... but could you comment on the first? I am aware of the adage that we can't change anyone but ourselves... but is does this really imply that we shouldn't try? Or do you think this is only the case for a sensitive relationship like husband/wife?

I understand that you can lead a horse to water but can't make it drink; to shove it's head in the water would be to drown it (or get kicked pretty good). But... if water = rationality-increasing ideas/concepts/arguments, is there anything to be said about making someone well aware of the existence of the water if they get thirsty?

Put another way, that is the point of evangelization or "rationality outreach"?