To Go or Not

Today you started out with wondering if you should go to your ex for Christmas or not.

You told me that if I asked you not to, you would not go.

I told you I would not make that decision for you.

You said you would not go.

I told you you had given your word and you should keep it.

You said ok.

Sadly, on the drive up to your ex's place, you changed.  You became distant and cold.

Why?