Science is about looking at things, making guesses about them, and then figuring out how to test those guesses. A huge portion of that testing requires measurement. To compare two things, such as two states of being separated by time and work, you need a basis of comparison. These measurements and comparisons form the basis of the study, and if they are useful, allow us to test our guesses, our hypotheses, by changing things, and then seeing what the measurements look like.
Most of the measurement we see in a given week is pretty simple. Can we fit the car in that space? What size shirt do I need? How much milk goes in this recipe? Things get a little more complicated when goals become less anchored in the physical world. How important is it really that Kid 2 is a bit taller than kid 1. They might think it’s very important, and maybe you think it’d be good to fudge the difference in the service of family harmony.
There are two particular areas of measurement which are particularly hard. One is at work. Some jobs are pretty straight forward, such as piecework tasks. They have a few confounding variables which can be relatively easily eliminated, such as differences in tools or work area. Other jobs are far harder to measure, such as engineering or art jobs where one must first devise a solution to a problem that maybe has never been solved before. Measuring the relative productivity of such a person can be quite difficult, especially in a shared office where their interactions with others might also have an effect on themselves and others.
The other hard area is measuring ones own progress in life. This is a topic we shall attempt to explore at length on this site. First we shall attempt to define measurement as it applies to humans, and then we shall try to come up with a straw man list of aspects of oneself which could be reasonably be measured.
Measurement. To observe a describable state in terms can unambiguously be compared to other such observations.
Some simple measurements are height, weight, age, strength. Given a reasonable test, these can be reduced to a set of numbers.
More complex measurements: what skills do you have, how good are you at them. What do those levels mean?
What resources do you have? Money (easy to count). Liquid assets (easily converted to money). Other assets, such as tools, which maybe you could sell for money, but maybe you could spend time, and use the tools to make money. Influence. Who can you get to help you, and how well can they help?
Note that these last three can be very hard to measure the final output of, because in some ways they all can be converted into each other, but the results from that conversion can be highly variable.