I had a professional interest in metrics, when I worked in software, and I maintain a vivid amateur interest in the subject. I measure lots of things: my exercise, my food intake, my moods. How long it takes to get places. How long it takes to do chores. The rate at which I'm learning Chinese characters, and the rate at which I'm forgetting them.
I like measuring things because it brings to light misunderstandings. Human beings excel at detecting pattern and form. We are not so good at quantity and scale, and the mistakes we make there can cause a lot of difficulty.
Martha and I once made a list of all the projects we wanted to do around the house. We then estimated, independently, how many hours each project would take. The results were illuminating. My estimates were usually three or four times greater than hers. As we talked through our estimates, we learned a great deal about how we think of work and time.
I would count in things such as, "we probably won't be able to find the right stuff at the hardware store. We'll have to come back and plan it over, and go to the store again when we know what's there. So that's another two hours." Or, "something will get screwed up at this point, and we'll have to do some of it over, so I added another day for that."
"What will get screwed up?" Martha would ask.
"I don't know. Doesn't something always get screwed up?" I'd say.
Then we tracked, for a while, how long these things actually took. The time usually fell in between our estimates. Martha generously conceded that they were usually closer to mine than to hers. But when mine were off, they were sometimes wildly off. I would allocate days to a half hour job.
It was good to get a better sense of how long things would take. But what was even more valuable was getting some insight into how our expectations diverged. Why was Martha willing to take on things we didn't have time for? Why was I so miserly about time, so unwilling to commit a few minutes? Well, because we had different projects in our minds' eyes.
And we had different senses of what "counted." I would double-count store trips; Martha would fold them together. "We'll be going to the store anyway. We can get that on the way."
True enough. But Martha allocated no time for mistakes, backtracks, do-overs. I habitually added half again for "the things that will go wrong."
"But what could go wrong?"
"Something always goes wrong," I'd say. But actually that's not true. Sometimes everything works. I have a really unreasonable dread of overcommitting my time: I'm nervous if time-commitments don't have an hour or two of insulation between them. Sometimes it's not very important to be exactly on time. Allocating an extra half hour in order to be completely sure of not being five minutes late to a casual lunch date is not, actually, good planning.
Anyway, my point is that this is the sort of thing you learn by actually measuring things. The process of measuring is, itself, a process of discovery, a way of investigating your assumptions and expectations.