You’d be surprised to what degree artists still tell themselves “you cannot do this” and “you cannot do that” notwithstanding the anything goes atmosphere of the art establishment. So it’s always important to stay grounded in human nature, one’s own nature and that of the world.
The only things you can’t do are the things that you really can’t do. For instance, let’s say you want to draw like Ingres. The “modern” side of the art world says, “you can’t! it’s already been done!” The reality aspect of the task says “you can’t” because you’ve tried and have discovered that it’s really hard to draw like Ingres drew.
Here’s an Ingrist-aspirant moment in my notebook in the form of a very linear drawing of my own foot — and people think that I’m only about koi!
If you want to draw like Ingres, perhaps you persist despite the slings and arrows of outrageous fortune because your desire is strong. If luck is with you, and your desire is plucky enough, you won’t draw exactly like Ingres (because he was a unique individual) but perchance there comes a day that you draw very precisely. And you wake to the possession of a strong skill so that afterwards you can draw with great confidence and penetration.
If that happens, you have such a marvelous challenge ahead: you must learn then to draw like you. It’s like waking up in the morning as a child and seeing that the world is there. What will you do with it?
Moral of the story, do not heed the do’s and don’ts!