That sounds more like a mental thing than anything else. Does this happen to you whenever you play in tournament or during friendlies too?
A big part of playing with people who are going ham and playing competitively is knowing what they can and can't do and then taking a massive chill pill. If you know the limits of their character, you can begin to focus on what their options are for pressuring you and try to read which option they choose before they choose it. Do that, and you turn their aggression into your own advantage. That kind of ability is really important to playing Charizard against more fast paced characters.
But taking a chill pill when you get to the tournament or pick up the controller is actually even more important than knowing how to play the game or MU. You can't act on or acquire new knowledge very well without a clear mind. For some people, it helps to take deep breaths. For others it helps to tell themselves comforting things (see
Muskrat Catcher
's post). Some even try to zone out and forget where they even are or what they are doing. Everyone has some way of coping when they feel overwhelmed. What do you do when you take exams and they are in your face (you seem to be in college)?
As far as what you can do going forward and over break, just play the game. I recommend going to Anther's Ladder so that you can be sure you get reasonably good opponents. This can also help with your ping if it is occasionally a little spotty because you can determine who you want to play based on geographic location. But be sure to
save your losses. Watch what you did, find where you messed up, and don't do it again. Write it down if that's helpful to you. Whatever it takes to not make the same mistake twice. If you need help analyzing your gameplay, feel free to post it in the videos thread or this one and I'm sure the board will help.