Happy Monday!

It was in the morning on Monday. I was sitting in the office when Dr. F came in.
He said, “Good morning. How are you?”
I replied, “Fine. How are you, Doctor?”
He said, “Good. How was your weekend?”  
“Oh, it was very nice!” 
 Then he said, “Happy Monday!”
I answered, “Not that happy. You know, it is the first day!”
He smiled and told another co-worker about our conversation.  All of us laughed, and I said, “Now, we are happy! I was kidding.”
Dr. F said, “Oh, you were joking. If you are not happy, no joking, please let us know. We will help you.”
“Ok, Doctor. Thank you!”