Commas, Part 9
Rule 1 – Use a comma to separate a statement from a question.
Example: I can go, can’t I?
Rule 2 – Use a comma to separate contrasting parts of a sentence.
Example: That is my money, not yours.
Pop Quiz
Select the correct sentence.
1A. You’re Marvin from my old Denver neighborhood, aren’t you?
1B. You’re Marvin from my old Denver neighborhood aren’t you?
2A. I believe that’s my jacket, isn’t it?
2B. I believe that’s my jacket isn’t it?
3A. That is a mountain lion not a house cat.
3B. That is a mountain lion, not a house cat.
Pop Quiz Answers
1A. You’re Marvin from my old Denver neighborhood, aren’t you?
2A. I believe that’s my jacket, isn’t it?
3B. That is a mountain lion, not a house cat.
Posted on Tuesday, February 19th, 2013, at 2:45 pm

I would like clarification for this type of sentence if a comma should be used when you are saying “not this, but that”.
Picture it not only in your minds, but in your hearts.
Should there be a comma separating contrasting parts of a sentence?
Yes, that is very much in line with our GrammarBook.com Rule 18 of Commas: “Use a comma to separate contrasting parts of a sentence.” The comma in your sentence is correct. Also note that, in American English, the period should always be inside the quotation mark.