A story that fails to provide challenges for its characters does not deserve to exist. Too many stories fall flat due to the soft treatment of their characters. Obstacles drive stories. In general the crueller these obstacles are, the better. Be cruel to your characters by threatening what they treasure most dearly. This isn’t to be sadistic—it makes your characters more likeable, relatable, and gives meaning to your story. Your audience will grow to respect you because your plot’s unfortunate turns make it appear more realistic.