Just because someone is pulling a face at you, sending off negative vibes in spades does not mean that you should reciprocate. You have the power to choose how you react. You could take it as a hit to you or you could let it slide. Most people are aware of this but it is quite hard to do the latter when you are feeling a little bit guilty. Deep down you know that you have somewhat played a part in the exchange so you are conflicted. Dwelling in this will only get you stuck further. Forgive yourself and move forward. Express the frustration out. You might not want to do this with the other person so perhaps writing it would be a better alternative. After you do that, decide to rise above the situation. Plan on how you are going to do that and get it done. Take small steps in that direction and focus on doing it with discipline and persistence.