How do the connotations of a word determine its effectiveness in speech and writing?

Connotations are words or phrases that are associated with the connoted word. As to how do these connotations of a word determine the effectiveness in speech and writing when using words with connotations, they simply give spice to the content. Sometimes they become the perfect word to be utilized to make the sentence deliver more impact and instil to the readers that it was an important event in the book. As for speeches, it makes the curves and turns, the jumps and falls of the flow of the speech. This would either make or break the whole thing when misused.