Is it grammatically correct to say:
"I can't tell you it because it is a secret".
This sounds better:
"I can't tell you that because that is a secret".
But if I break the first sentence, it is okay to say, "because it is a secret". As I am using "it" in this second phrase I believe I should use "it" in the first phrase also. But "I can't tell you it" doesn't sound right to me.