How do you know what to do?

This morning I replaced the float valve in my mothers toilet cistern because the old one was faulty, taking around 15min to fill the cistern. This afternoon I replaced the valves in our kitchen mixer tap, because one side had started leaking after about 5 years of use and under the very high mains pressure we have here.

I invited Chris to the kitchen to see what I was doing (just in case, y'know?) when she expressed the title of this post.

To me it all seems obvious, the knowledge of the principles behind how all this works having been acquired so long ago that I can't even really remember how I learned. Some of it definitely came from watching my father, some from trial and error as I tried to do what I knew could be done by someone skilled in the art (and wished my father was there to do it at the time). So it was natural to run my fingertip around the bottom of the handle on the tap, seeking the indentation that would tell me it was held in place with a grub screw. I expected to find isolation valves below the sink on the hot & cold feed to the taps, and they were there just as expected. The original valves came out with a sharp blow from my hand on the handle of the spanner to break the mild corrosion/limescale on the threads, rather than levering away on the spanner & causing additional wear/stress on the tap body. Then everything just screwed back together without trouble, a reverse of disassembly.

Its pleasing and useful to do this stuff - I'm just grateful that it all makes sense and isn't hard to do. I'm sure there's an illustration here about learning in other areas, often seen as us 'knowing' something in such a fundamental way that we assume it must a) be true, b) be self-evident and c) that everyone else should know it too.