Charlie wants to know for sure if what happened to Algernon will happen to him. His thinking proved to be correct and it really begins to set in that the same will happen to Charlie.
As Charlie lives his final moments of intelligence, he grows frustrated with himself because he can't remember the things he did only a few months ago.
Charlie is tired of what's happening to him. He writes in his last progress report that he is moving away from New York for good and wants someone to put flowers on Algernons grave. His search for intelligence turned out to be a detrimental path in the end.