In Chapter 11 of Sorcerer’s Stone, Harry plays his first Quidditch match. When he swallows the Snitch, he digests an assumption that follows him all the way to the end of the series—Professor Snape is out to kill him. Ironically (or not), it is Snape’s final gift to Harry of his memories that helps Harry unlock the very first Snitch he ever caught (well, swallowed) and find the Resurrection Stone.
You may have heard the saying that when we assume, we make an arse out of all parties involved, especially ourselves. In the end, Harry realizes his folly (his arse-ness) in not trusting Snape. That realization humbles his heart and prepares him to face his greatest adventure—giving himself to Voldemort to save his friends.
We all have those arse-y moments, but the key is that when we realize we are being a fool to humble ourselves and do what is right. Harry used Snape’s information to drive him forward in his mission to end Voldemort’s reign of terror. When he survives, he honors the man he falsely accused for many years by naming one of his children after Severus (and, I like to think, telling everyone the greatest part of Snape, his love for Lily Evans).
“Albus Severus,” Harry said quietly, so that nobody but Ginny could hear, and she was tactful enough to pretend to be waving to Rose, who was now on the train, “you were named for two headmasters of Hogwarts. One of them was a Slytherin and he was probably the bravest man I ever knew.” ~ Harry Potter and the Deathly Hallows
When pride comes, then comes disgrace, but with the humble is wisdom. ~ Proverbs 11:2 ESV