It started with The Story of Us (1999-Willis, Pfeiffer).
The meat of the film is the implosion of a marriage and a painful separation. But the dessert (and gift) is the introduction of a simple ritual: at the end of the day, everyone at the table tells the rest of the family his or her high and low moment of the day. Since then, we have participated in this ritual, on and off as a couple, and now with the kids.
The result is surprising insight into your spouse/child's character. What causes the greatest daily joy and satisfaction? What frustrates, annoys, and casts a shadow on the day? Is A more impressed by what we did or what was said? Does Z remember past an hour ago, and if so, what play activity is his favorite? Mommy has accomplishment-based highs; Daddy has things-going-smoothly concerns.
This year I'm recording our hi/lo's. No pressure; we miss days here and there, and sometimes we can't squeeze a lot out of Z. But I think some day in the future we will look over this history and smile.