There is a wrong common belief that goldfish only have memories last for 3-7secs.
In fact, scientists said their memories can last long to 5 months!
So our Mr. Goldfish is suffering in his short memory, the dialogue is here below:
"Oh, I'm so happy!"
"Why I'm so happy?"
"I forgot everything..." (Cried)
~~~ 7 seconds past ~~~
"Oh, I'm so happy..."
(Repeat and repeat into an infinity loop)