A short story is confined to one mood, to which everything in the story pertains. Characters, setting, time, events, are all subject to the mood. And you can try more ephemeral, more fleeting things in a story - you can work more by suggestion - than in a novel. Less is resolved, more is suggested, perhaps.
Eudora WeltySince we must and do write each our own way, we may during actual writing get more lasting instruction not from another's work, whatever its blessings, however better it is than ours, but from our own poor scratched-over pages. For these we can hold up to life. That is, we are born with a mind and heart to hold each page up to, and to ask: is it valid?
Eudora Welty