A simple way to measure up/down trends in day-to-day life

Evaluation requires measurement. Personal evaluation requires personal measurement.
I keep a journal using the “Bullet Journal” method. To this I have added an addition for personal measurement.
The Bullet Journal has you put an index for the days of the month at the start of the month, as a form of a calendar. I do that, but then to the right of each day, I add a single numeric index that tracks how well the day went.
+2 “The Best Day Ever”
+1 A better-than-average day, with some bright spots.
0 Just a run of the mill day, not too bad, not too good, not remarkable.
-1 A worse-than-average day, perhaps grey or sick or down or low energy
-2 “The Worst Day Ever”
The beauty of this particular system is it’s not too difficult to figure out. I tried for a while to track specific mood types, physical situations, etc., but realized it was just too hard to make all those measurements, especially at the end of the day. Bad days tended not to get tracked. This system is instinctive. “The Best Day Ever” and “Worst Day Ever” were inspired by my youngest son (who’s 10). When he was a bit younger he would often say “This is the worst day ever” or “This is the best day ever” – big extremes in response to things happening that he liked or didn’t like. I would sometimes comment, “I really hope this is the worst day you ever experience” – the point being that if you have your worst day at age 8, the rest of your life wouldn’t be too bad. Obviously, we’ve all been there: “worst days” and “best days.” They are easy to know. The +1/-1 are there for days that are slightly positive or slightly negative but don’t qualify as “bests” or “worsts.”
Why do I track all of this? Because it’s easy at a glance to see a stream of reflection on the past 30 days. This day might seem awful, but looking in the chart, I can see it’s just a one-off. I can look back and remember that day, which was a “best day.” On the other hand, I might see a pattern: a bunch of -1s could be leading up to a -2. Is there some way to disrupt the pattern? Is there something that’s causing it? Is there something that needs to be addressed?
Do you have some method for tracking your own personal ups-and-downs, goals, etc?