Why is Xander Sad?

Xander acted sad all morning, the tiniest thing would set him off. Not a good start for the school day. So, when I dropped him off at school, I mentioned to one of his teachers, "We're feeling sad today." At this point, Xander let go of my hand, walked towards the teacher and said, "I'm feeling sad." and his lower lip was puffed out. The teacher gathered Xander up into her lap and asked Xander why he was feeling sad. Tears were streaming down his face as he answered, "Because my Mommy yelled at me."

P.S. I had yelled at him in the morning during breakfast as he scraped his cup along the floor upside down. Guess it ruined the whole morning for him!