Figure out your default mood. It’s the setting your day starts on unless you change it.

Everyone wakes up somewhere on a scale, and the starting point differs from person to person. If yours sits low, the ordinary events of a morning get read through it, and by lunch it seems like the day caused the mood when the mood was already there at seven. Knowing your default does not fix it, though it does stop you blaming the wrong things and reading a normal Tuesday as evidence.

Note where you start for a week, one word each morning before anything happens. Watch how often the day matched it. Then look for the small thing that reliably nudges the number.