I don't know if it's a normal reaction but it at least seems logical to close your heart to people that you think will hurt you in the long run. I had a similar story to yours, or turning point in how I react to things. I am very shy but I have to act extroverted when I am working. I had a very long and tough week this time which worsened my stutter considerably. I had to push through it and talk because I was supposed to teach somebody I did not know well how to do something that day. We worked together and he laughed in my face and said some rude and ignorant types of comments and my reaction wasn't even to scold him it was just a very sarcastic and hollow type of "ha . . . ha". I spent the rest of that day realising that the thought of interacting with him made me feel sickened by him and I left our interactions very short and blunt. Afterwards, when I went home, I thought more about it and realised that, instead of feeling bad about myself, I felt worse that somebody can be an adult who is so childish and boundlessly stupid. Every other interaction was marked by that same opinion and I never had any desire to be friendly to him again but I never mistreated him or loathed him for it either. The way I see it, people aren't entitled to anything from me. If they choose to close the door on any possibility of you liking them, you have no obligation to keep opening it again just so they can slam it in your face another time. People who are inclined to mock this will always hold it against you, even if they say nothing ever again - that's why I don't care.