I had a good day yesterday, so I wanted to deconstruct it. Today is much less good, maybe for the same reasons yesterday was good.
What was good yesterday:
social interaction - made a few phone calls
writing for a full hour in the morning
walking in the sun
I got a bit of sun today (a few minutes, without walking), and some social interaction - too much, which made me cranky and irritable.
There's no conclusion here. Only an observation that a combination of good deeds seems quite likely to make you happy and creates a postive cycle where you're encouraged to do more good things.