I thought I could get away with it. They looked ok in the preview. I submitted them without post-processing. Now I have over 100 images rejected for things that would have been fixed in post-processing: noise, color, composition, etc.
View files at 100%. Always. Don't try to speed through it.
If you think it needs cropping, it does. Take the minute to do it.
If the contrast looks okay but not perfect, go ahead and adjust it.
There are penalties for going too fast.
Photo credits: Natou98.