In general, your readers want to see your characters succeed in the end of the story. Whether their end goal is a romantic relationship, a mystery solved, or a victory over the forces of evil, your story’s characters should eventually achieve it in one way or another. However, if you want to make you story really satisfying, your characters will need to encounter some serious obstacles on the way to getting what they want. Part of your job as a writer involves throwing a wrench into your characters’ plans at the worst possible times.
Some of the problems your characters encounter will be products of chance. A storm might strand the characters in a strange place, for example, or a flat tire may cause a delay that leads to disastrous consequences. Although you might annoy your reader with long strings of unlikely coincidences or improbable events, it’s perfectly acceptable to use a chance occurrence as a way to set some of your plot events in motion.
Chance events aren’t the only forces that should come between your readers and their ultimate goal. The schemes and actions of your story’s antagonists should also manage to throw a wrench in the protagonist’s plans for success. These characters don’t have to be chessmasters who plan out intricate chain reactions of events; in fact, something as simple as blackmailing a protagonist or trying to seduce someone’s lover can cause enough turmoil to sustain the plot of a novel.
It might be a little harsh to say that good storytellers have a knack for ruining their characters’ lives, but it’s essentially true. Making it too easy for your protagonists to get what they want can bore your readers and leave you with very little to write about. Instead, use a combination of chance occurrences and antagonists’ actions to make your characters work for the goal they want to achieve.