Religious Symbolism in Language

Those who know me also know I am not a religious person. Normally I don't mind being told "God bless you" and respond with a somewhat shy "thank you", just to be nice, but some expressions in some languages make me relatively uncomfortable. In Southern Germany, "Grüß Gott!" ("Greet God!") is a very common greeting. I don't live in Southern Germany, but I simply cannot picture myself saying that.

I have always avoided expressions with obviously religious connotations like "Thank God!" and "God willing!", while I don't have much of a problem with originally religious expressions that have diachronically lost their primary meaning, such as "Good-bye!" ("God be with ye!") and "Adieu!" ("To God [I bestow your destiny]!").

The ones I have problem with are those expressions with obviously religious connotations in languages that have no alternatives whatsoever. If I want to avoid saying "God bless you!", what should I say to an English-speaking someone who has just sneezed? In Persian, what should I say while departing if I don't wanna say "خداحافظ" ("Chodā hāfez", "May God be your guardian!")?

Other examples include:

Icelandic: Bless! (Good-bye)
Arabic world: In sha Allah! (God willing)
Portuguese: Nossa mãe do céu! (Interjection that expresses surprise or fear, "Our mother in heaven!")
Greek: Θεέ μου! (Oh, my God!)

Language and culture are permanently intertwined, and religion is a (very important) part of many cultures around the world. As some parts of the world become less religious, their languages slowly part from more obviously religious connotations, while such expressions are emphasized in parts of the world that gradually become more religious/fundamentalist.

What is your take on this? Are you religious? Do you deliberately use expressions containing religious connotations?