First Amendment WTF?

I am an atheist and appreciate that the Constitution protects my right to be so... First Amendment... Which, I take to mean that the government cannot force you to practice a religion of its choosing nor interfere with your practice of a religion of your choice, or choosing to not practice one at all. So if I'm correct about that…then where, exactly, does the Department of Veterans Affairs get off telling anybody they can't say "God bless you" to the family of a fallen soldier?