In English there are a couple of sayings that I think about at times:
A little knowledge is a dangerous thing. Or: I know just enough to be dangerous.
When it comes to learning a new skill, there are levels of knowledge. When you don't know what you don't know, you don't know that you don't know it.
The danger is that as one begins to learn a little bit, the assumption is that you know more than you actually do. A student has a few experiences, draws conclusions based on those experiences, then extrapolates that limited experience to the entire body of knowledge - which they don't know and can't in some cases, even begin to comprehend.
Then they get set in their ways, assume they know The Answer, become reluctant to listen to anyone else about how things might not actually be the way they think it is.
The problem then becomes the repetition of the information that is incomplete at best, or just plain wrong. When corrected, sometimes the person does not react well.
When they go outside of their comfort zone, scale up in some way either by making longer/wider warps, use a different quality of yarn, or a different fibre, their results may be less than what they desired.
At times I have then seen the blame being assigned to the yarn (it was 'bad'), the equipment (it was 'bad'), the advice they were given (which may have been ignored) - anything but accept that their process may have been at fault and needed to be adjusted to accommodate the changes to their regular routine.
When I advise people to apply a hard press, I've been told that it isn't necessary. That if I'm getting iron tracks on seams, I just don't know how to press a seam open properly. I've been told over and over again that wet finishing is just 'washing'. I've even been told that it isn't necessary. Which it may not be, depending...
I've been told that my advice on ergonomics or processes/efficiency is just plain wrong. That somehow their X years of experience supersedes my 44+. All I can say to them is, you do you. If it's working for you, then that's what you need to do.
One of the things I learned very early on was that becoming a weaver was going to be a life long journey. That has turned out to be very true. As I change my life, change my focus, change how I approach the creation of cloth, I look forward to continuing the journey of learning. Of gaining more experiences to add to my foundation of knowledge. I still explore, take workshops from other weavers - because their experience is different from my own - buy books, read magazine articles. When I discover that I have been wrong about something, I add that to my growing - ever growing - pool of knowledge.
I still make mistakes. I still learn. I find that exciting.