I don’t know who exactly came up with the word “coronacoaster” but there are definitely days when it’s entirely accurate. I can swing from being perfectly fine to frustration, anger, deep sadness, happy crying, over-enthusiasm, and mostly back to fine again. And that was just Tuesday!
The main thing is that just about everyone is going through this daily. Patience and kindness go a long way.
The other thing to remember is that all things must pass, including bad days.