Two or more short sentences add cadence. They
also separate ideas that would otherwise be more closely linked by a conjunction
in a single sentence.
Literature is invention.
Fiction is fiction. To call a story a true story is an insult
to both art and truth.
The period after
invention stops the reader momentarily, abruptly separating what
follows. Compare the effect with: Literature is invention, and
fiction is fiction. Far less clear that you're dealing with two
separate ideas, not two linked ones.
Busy on two phones
at once trying to stem disaster, you had no time to turn and look.
You didn't need to. You felt him.
We detest both words. We spit them at each
other with the fury of hissing geese. We duck and dodge them.
I came. I saw. I conquered.
Of course, Cicero's tricolon for Caesar.