I have forgotten how many times I have taken a sink trap off and poured the trap water down the same sink and soaked everywhere including me. Still do it. I remember going to a job once and spending hours bending the pipework to get it to go into a tee piece, to be told that if I turned the tee another way I could have done it using half the pipe and virtually no time at all. Talk about feeling a plant pot!!!
Seems I learnt most of what I know from mistakes I have made.
It took me yonks to learn that the screw, drill bit and plug must all match to get a proper fixing.
Mind you as you get older you tend to remember what went wrong last time you did it and so try to avoid making the same mistake, also you learn to allow for things going wrong in your time estimates.
The thing is, as you get older still, you start to forget or some of us do and back you go to start all over again. Hee! Hee!