Have you ever tuned a musical instrument? Take a guitar, for example. You play two adjacent strings. If you fret the lower, bassier string in the right place (generally the 5th fret, with a single exception - don't worry if this makes no sense - on the B string, which is usually fretted in the 4th position to tune the next string to E rather than F), the two strings should play the same note. Now, they will not actually sound the same. The strings are different thicknesses and they're positioned differently on the fretboard, all of which will lead to different overtones. Though the resulting sounds *will* be different, almost everyone will be able to tell that the notes are the same, and typically they won't be aware of those little sonic (overtone) differences in a performance.
Until they have to do the tuning themselves. Then it can be difficult - much like hearing that a sung note was hit (or not) versus singing it oneself (which takes practice).
What usually happens is that you play the two strings together (appropriately fretting the lower one for the same note) to compare the sounds, then you adjust the higher string until both strings sound the same - which you can feel as a sort of relaxation, as the two sounds stop clashing and merge. But you won't be sure. So then, guess what? You intentionally mess up your work: you retune that same string a little higher or lower, until it definitely sounds out of whack. And you do the same in the opposite direction, going out of tune on the other end.
Basically, you figure out what position to turn the tuning nut to so that the string is definitely too high, and then on the other side, what position is definitely too low. Now you have a tolerance range. In between those two out-of-tune angles of the nut (amounts of rotation, similar to clock hand positions), you have some wiggle room. Some of that wiggle room, if you pay close attention, will also sound a bit out of tune. But just hearing the two ways your tuning can be wrong (too high, too low) brings immediate clarity to the process. And in a pinch, you can simply turn the nut to about the middle of that range, a trick that's unlikely to fail. It will sound surprisingly good and solid and tuned, simply because you picked the spot halfway between "definitely too high now" and "definitely too low now."
This sounds very specific, doesn't it?
What if I told you that much or most of life is something like this tuning process?
The universe is made of signals - waves - cycles - circles - orbits - vibrations.
Almost everything is tuning.
When you learn something, your neurons are tuning.
Does it look like the two strings of a guitar, and the too-high, too-low, find-the-middle-of-those process? Not outwardly. But inwardly? Maybe.