In his book Abstraction in Art and Nature, Nathan Cabot Hale (what American Revolutionary names!) explains to us that abstraction is the representation of the essence of things perceived.
He suggests graduated projects, starting from the very ABCs of drawing. That makes his book perfect for deliberate practice.
He points out that the line does not truly exist in nature (as Mother told me long ago), and then we practice the four basic varieties of line:
2. curved (PLUS 1,2 subsets: straight then curved, or curved, then straight)
4. line weights
Of course all these basics can be combined, and are, in drawing. I spent a very satisfying hour reading, listening to BrainBaths on the iPhone (Superlearning tone plus the sound of water), practicing drawing lines, stick figures, and finally my drawing projects, a quartz crystal and my hand, both of which models were willing and readily available.