Why can't I just let it go?

I've been blogging on here for nearly two years and most of the time I'm fairly level-headed. Even when I'm on Omegle or the Thinking Atheist, I generally stay patient, so it might be interesting to learn that my patience seems to wear off when I'm with my theist family members.

There was a period when I got away from writing on here and I even left the forums; I like to refer to this time as my acceptance period, but that period is over and I'm trying to be active again.

While I never have been religious, my deconversion really didn't come until about two years ago. That process began when my family (mother, SIL) started going off the deep end with their recommitment to Catholicism. Their overzealous attitude and claims of daily miracles started to become too much for me to swallow. So I ratcheted up my investigative journalism training and dived deep into the questions of religion.

As you may know from earlier posts, I came out clean on the other side (just like Andy Dufresne in Shawshank) as a full-blown atheist. In the past two years, I've had some debates with them, mostly via email with my SIL (those have been well-documented on here), but we got to a point where we calmed down and didn't talk about it anymore.

Every once in a while, though, my mother will bring up something peripheral about religion or morality and we end up debating/discussing/arguing. And this is the crux of my post here: Why can't I just let it go?

And I tend to lose my patience when we discuss this stuff. I'm so patient with virtual strangers, yet when I'm with my mother, who is 74 and not exactly the healthiest person, religion always works its way into our conversation and I always end up losing my patience with her until she taps out. Whenever she hears something completely rational from me and it makes her think for just a split second against her dogma, she runs (metaphorically of course).

I think I'm impatient because I'm let down by her ignorance. In most parental-child relationships, you grow up idolizing your parents, thinking they are basically superheroes. But as you get older, you start to realize your parents are only human. And with my parents, they are starting to succumb to irrational behavior, and I'm not just talking about religion. As an atheist, I am very aware that this is the only life I have and the only life I'll have with them.

So why can't I just let this go? Why don't I just bite my tongue and listen to the bullshit? Why can't I ignore the "Praise Jesus" exults and the "GOD bless you" wishes (petty I know)? Even when we're having a non-religious normal conversation and I mention something that seems remarkable, my mom will say, "Swear to god!" She is so engrained in her ways that I just can't help myself when I get the chance to give her some info to which I know she isn't privy.

My mother and I have always butted heads about mundane bullshit and it has never affected our relationship. It's almost how we communicate. If it's not an argument then it's not important enough to discuss. But when it's religion, all the wheels fall off of the vehicle.

Finally, I think my urge to always want to discuss this with my family is because I grew up in a household where my parents wanted to know what was going on in my life, what I learned in school or at work, etc. Secularism is very important to me and I hate seeing so many people succumb to these lies and practices. So when I'm at my parents' home, I want to tell them everything that I've studied/learned because I know they have no idea these things exist.

But shouldn't I be able to to just let it go? It's been more than two years since I "came out" and yet the resentment and need to be right is not fading at all.

Thanks for reading.