One of the best pieces of advice I’ve learned as a writer is to make your characters suffer.
If your protagonist’s life is as sweet as a peach, who cares? If no one steps on her toes, if she has no flaws, if conflict is mild and everyone gives in and makes up easily—who gives a flying fig?
Yes, it’s hard to make your characters suffer. If was hard for me to write about Tess losing her baby brother. Hard to place slave catchers in Seneca Falls. Hard to make Lucy start all over again.
But readers invest in characters who know hardship. They keep reading because they want to know how—or if—these fictional people survive.