Setting a single line of type by hand takes longer than writing the whole paragraph it belongs to. That slowness is the lesson.
Every space is a piece of metal
On a screen, space is nothing. In a composing stick, every gap between words is a small block you have to choose and place. You start to see spacing as a decision rather than an accident.
What carries over
Back at a computer, the habits stay: tighter word spacing, fewer typefaces, more attention to the line that ends a paragraph alone.