There is a lot of knowledge you can't write down since you yourself don't know what it is, you just know how to apply it. For example, how do you structure your programs? You can write down some rules of thumb, but you can't write down your entire decision process as a flow chart that can be used on any program to structure every function in them. How to structure big programs is one of the biggest hurdles for new programmers, they just have to learn it themselves since nobody can teach them that. You can get a bit of feedback for simple program structures, but for more complex cases you wont even get good feedback, to continue to improve at that stage you just have to rely on yourself.
There is so much software out there in a way it is not too different from biological systems. Programs are like creatures you can study and observe. There is no single book explaining all of software. You must be a bit of scientist yourself. Discover how thing work and what works best.
