You’ve engendered, given traits, and brought your characters to life on the page. It’s not surprising that writers find themselves attached to their characters and are afraid of putting them into complicated situations.
If you’ve created complex and compelling enough characters they will falter and they will hit obstacles. You’re writing a book not a description of the type of friend you’d like.
Think of the most memorable characters in fiction. Jay Gatsby. Elizabeth Bennett. Holden Caulfield. Lisbeth Salander. None of them are perfect. Perfect characters are 2D and forgettable.
It’s a writer’s job to depict compound problems and introduce character suffering. With complexity comes reader investment in the way they overcome obstacles. When characters are treated too nicely the story moves along just skimming the surface instead of plunging into deeper meaning. A deeper investment in the outcome of character drama will produce high-stakes tension for readers.
Tip for the revision process: “You not only don’t have to treat your characters nicely, in revision you should look for ways to make the obstacles bigger, the complications seemingly endless, and their suffering worse. Avoid the temptation to rescue your characters.” Manuscript Makeover: Revision Techniques No Fiction Writer Can Afford to Ignore, by Elizabeth Lyon