I have come to realize that there is a inherent hierarchy, when it comes to practicing the micro-skills, that make up the macro-skill of doing art.
These micro-skills are:
There are definitely more, but for me, this is sufficient. Also, each of them has sub-categories (i.e. Hue / Chroma / Temperature ... when it comes to color).
The hard part is to juggle them all, when making a painting. I know I have struggled a lot through paintings, because I tried to do 2 or more things at the same time.
So instead now I am trying to focus on each micro-skill and train it seperated. This is one aspect of something that is called "deliberate practice".
You can read about it here:
So in order to get better at composition, I went to the museum and made small (ugly) simplifications of the master-pieces that were on display there. After doing these simplifications I tried to find hidden structures beneath the painting, as you can see on the sketch und the lower middle. It was super-fascinating to find these hidden lines and rhythms.
I know these sketches are really basic. But it is this basic stage, that I neglected before and that made me struggle through the paintings a lot.
Before I did photo-copies, where I wanted to get everything exactly as in the source. I now realize that I was training too many micro-skills at the same time, which made growing my skill slower than it had to be.
Please tell me in the comments, if you are struggling with studies a lot or if you had a moment where you found a similar way of practicing.