So in panels three and four, you can tell exactly what Greg is feeling. He knows something is about to happen that isn't good and he is trying to brace for it. Then in the fourth panel his heart sinks completely.
It's a real feeling, the whole comic. It really hurts and I feel bad for him.
How he ended it hurt me the most too. How he stopped calling Twilight, "Twi" and changed it to, "Miss Sparkle."