Close Blender and go do something else for a while then come back to it and look at reference images (if possible). That will refresh your mind so that you can more easily spot problems.
I use references, I try to find the reference that happens to contain something that looks very similar to what i want to achieve. So I am talking about really small part of reference image or just an overall element, to help identify the specific of what i want to achieve then i can directly compare my render with that reference image and see what is wrong.
Yeah, reference images are good. Or, looking at a similar material or object in real life can help, too.
Often problems with realism come up because we try to reproduce the overall effect at a high level with a shader or texture. However, we ignore the small details that create the overall effect.
Sometimes if you start with the very smallest details and work your way up, it can help realism. In other words, try zooming in much further. If it looks right when you zoom in, it should look right when you zoom out.
The point of learning is to understand, how you do that is completely up to you. Through millions years of evolution people have been learning thing through billion of not trillion diffirent ways so as you will imagine none can tell you the “correct” way. The brain is extremely versatile.
Myself I am a big believe into the primitive way of learning, what people call “hands on approach”. That means I learn mainly through practice and depend way less on books and tutorial, I love to discover structures, finding relations between things , experiment and making a lot of mistakes. I find mistake extremely valuable into the learning not only the “What” but more importantly the “Why”.
Tutorial wise, it depends on the subject, if I dont know anything about the subject I watch a video tutorial, if I know something about the subject then a video tutorial is very slow for me and I prefer online documentation or some book, if I know a lot about the subject then experimentation is way faster for learning because it allows me to focus on exactly what I want. If I read a book or watch a tutorial, I do it step by step each step send me to blender and I try myself to recreate what I have just watched and read and even experiment a bit with it to get a good feeling, then a repause the video or continue to read the next page on the book.
I also keep a notebook by my side with ideas and observations, I really like to approach problems a lot more like a scientist that means I write down observations, formulate theories and hypothesis, do experiment and repeat the whole process.
This has worked for me for over 3 decades now into learning school stuff, studying law for my LLB and LLM degree , being a lawyer , learning electronic music , learning coding for most popular languages out there and finally now learning 3d graphics.
This process for me is fun and efficient. Yours may differ, the main goal should be that the learning process is to keep things fun and enjoyable.
PS: just because we do 3d graphics does not mean that anything we learn should be 3d graphics orientated , classical arts have a lot to teach and studying classical artists is define a great source of learning. Find a favourite artist and studying his or her style can be a great source of both inspiration and understanding of art. But of course in the end it comes down to the fact that you put the time and effort into learning and thats more than enough.