You’ve written your story. The protagonist is complete. She faces her fears and wins. Love conquers all. Business is good. The house is purchased and the yards tended.
What more does your story need?
How about bringing in a new character? If your character is a happy-go-lucky fellow, then make the new character a dour, oft-depressed individual.
Say your protagonist is a moody teen, then give him an optimistic classmate who just moved into the school.
Putting together diametrically opposed characters adds tension. They won’t always agree and so will sometimes argue…or ignore each other. Such conflict forces the protagonist to face her innermost fears. It creates turmoil and upsets the story details, often adding interest for the reader.
Your task is to take a piece that you’ve completed. Develop a character that is opposite to your protagonist in at least one major way. Insert that new character into the story in a time and place that surprises the reader. Finish the story, making sure that the new character maintains a place of importance.
At the end the new character can walk away…or the two characters can become lifelong friends. It’s up to what helps the tension in the story.
Have fun with this one.