When you write shorter pieces, the good and the bad can be more sharply defined. You don’t have time or word count to soften the edges. Maybe this is why my weaknesses become so much more apparent to me in shorter works. If I’m repeating the same phrases or words in an 80,000 word novel, they have more room to hide. But in a 10,000 word piece? It becomes obvious pretty fast. It’s hard to look at weaknesses without giving fodder to the inner critic. I try to keep it at bay by reminding myself that I can always edit those things out. And with each thing I notice and correct, I become a better writer.
Limiting my word count forces me to give even more thought to my choice of words. If you have a paragraph describing a character, then decide you need to cut it down to one sentence for pacing, imagine the difference in the words you would choose. Experimenting with word counts can sharpen your skills, expand your vocabulary, and increase your awareness of pacing.
Shorter pieces are like chiaroscuro. The light and the dark stand in much starker contrast and can show us where our strengths and weaknesses lie.