Some uncomfortable situations for atheists are when well-meaning friends and acquaintances use religiously-tinged phrases such as "You're Blessed" or "Praying for you" towards them. Following is an article that addresses these situations pretty well in my opinion. BTW, regarding the sneeze "Bless you", If I respond, I usually give a "gesundheit", which means, "To your health."
Atheists: Responding To The Christian Phrase “I’ll Pray For You”