Do you mean the difference between simple past and past perfect?
Simple past records a finished event, unconnected semantically to the present or any other point in time. Your first example is a typical and an excellent one. The story is finished-- end of story.
Past perfect records a past event which is meant to be represented as holding a relationship with another past-time event. Consequently, your second sentence is semantically incomplete-- it requires further information. For instance:
I had written a story only once when I was awarded the Pulitzer Prize.
Past perfect is relatively rare; when used, it is often unnecessary and should be avoided unless it is part of the association of two past-time events in the context AND their temporal relationship is unclear or needs stress.