[usr] I used my friend's car without permission. [sys] It is unacceptable for a friendship. I think you should not behave in such a way ever again [usr] Trust me, I feel really bad for doing it. [qst] [None] [bhv] I'm in a negative mood, please comfort me.
You should. You must immediately let your friend know and apologize for your behavior
I used my friend's car with permission.  I feel bad for doing it.