Our son noticed everyone's gloomy mood and he decided to try and change it. He remembered a conversation I had with him months ago about emotions being "contagious." I had forgotten that we had talked about "catching" moods, both good and bad, from other people. Earlier this year I brought up "emotional contagion" with our son because it was so frustrating for me to see one of our kid's bad moods spread to the other kid. Rather than joining his sister in her bad mood, we talked about how instead our son could use his positive mood to try and turn his sister's day around. If he was happy, his sister might "catch" that happiness and she might become happy as well.
After our son's reminder, I've started to notice just how often one of us "catches" another family member's or friend's positive and negative emotions. With a family of five it happens constantly!
I've also noticed that I have baby to thank for spreading many positive emotions day in and day out. Even in the middle of an argument, our older two kids will pause and start giggling with her as she rolls a ball, crawls backwards, or blows raspberries. It always puts a smile on my face to see our older kids "catch" baby's happiness. Thank goodness baby's happiness seems to be exceptionally contagious.