@ifmn16 Grammar is a terrible example here. You don't use grammar just by yourself, you use it to communicate with other people. The reason there's such a thing as proper grammar, is that we can all agree on it and communicate more effectively. What is proper can slightly vary by communities. It's true that some languages and structures are going to be more fitting to how some particular people's brains work, but if we're to use English among other people, type not like this do even if it makes more sense to you.
However, playing is something quite personal, and you're communicating with an inanimate object (well, you're kind of animating it, so to speak).
Saying that "how most people do it" is proper would be like saying that "liking chocolate is proper" in a society where majority of people like chocolate. I can assure you that a lot of people play way out of their comfort zone, because they have been taught to do it by teachers. It's very harmful. Hell, my teacher tried to force a left hand technique on me, that made it remarkably harder for me to move the hand around the fretboard. Whenever I used my flat hand technique, I could play more relaxed, faster, more consistently, etc. But he didn't like it and told me that technique had some issues (which didn't turn out to be issues with any material I played since I seamlessly curved fingers as needed, but kept them flat on the fingerboard by default).
But he didn't care, it wasn't "proper". I could play both techniques, but one was clearly superior to the other in my case. This flat hand technique that I'm using translated very well to a six string bass, since it lets me mute strings more easily, and reach B and E very easily, whereas if I kept doing what my teacher told me, my transition to a 6 string would be way more painful.
What "works for most people" is kind of irrelevant if "most" means more like "about 20%" and the other 80% prefer a myriad of different techniques, but no technique is preferred by more than 20% of the people, so there's still the most common one that's going to be forced down everyone's throat because it's "proper".
I come from classical piano and there certainly are ways that are more proper for the genre, but it has to do with execution and the end result, where using a more stiff playing hand might be a serious detriment. In jazz piano "throw your hands at the keyboard and see how it feels but also make it groovy without injuring yourself" is usually the norm. It's funny how the classical technique is way more focused on making a very niche, specific sound, while the jazz technique can be literally anything as long as you can express yourself and your teacher is flexible.
So instead of saying how most people do it is proper, it's more realistic to say that what works with (and not against) you is proper. Look at Marty Friedman, for example. He's a guitarist who holds a pick in such a way that I get honorary tendinitis when I watch him play. Yet it works absolutely fine with his hand in particular.
I went kind of over the top in this post, but this topic is very personal to me, because I was forced to do "the proper thing" for years and I was very unhappy with how I felt playing the instrument, and I finally reached freedom when I went from classical to jazz on piano, and started playing the bass. I picked up violin by myself, with only a few visits to a cello instructor, just to get the hang of some basics of how to actually bow the instrument. My violin technique looks very "improper" but it is very comfortable to me. I play violin like a cello and it looks ridiculous but it feels great. I just can't hold it on my shoulder comfortably due to injuries.
Only you know how you feel playing your instrument, so do listen to advice on technique, but also do it your way, just avoid injury and take precautions.
