Low days have patterns you cannot see from inside them. A two-week evening check-in by text, read the right way, finds the one thing that keeps showing up.

Day-by-day Gallup data shows Monday is no worse than Wednesday. What makes it feel that way is the drop from Sunday, visible in your own tracking too.

We matched CDC estimates of short sleep and frequent mental distress for every US county. The link is strong, and useful to anyone tracking their mood.

Who you were with predicts how you felt. We reworked a classic study of 909 women's days to show which company lifts mood and which drains it.

A way to track your mood in a few words a day, plus CDC survey data on how many low days a typical month actually contains.