New writers have a tendency to write characters who are unrealistically perfect. After all, if you’re female, wouldn’t it be great to have long blonde hair, perfect boobs, and big blue eyes that charm every guy around? And if you’re a guy, why not have a six-pack and awesome combat skills? This is fiction, right? We might as well have fun being these people.
And you might be able to pull it off. Unless, in addition to this, your character’s actions should have consequences—but don’t. Or if they do get into trouble, it’s never really their fault. And everyone falls in love/wants to have sex with them. And if someone disagrees with them, they’re always wrong. And even characters who shouldn’t need their help—do.
At this point you might have a Mary Sue on your hands. And the problem with Mary Sues is they’re not really interesting. We can’t relate to perfect people because we all know deep down that we’re not. And it’s the struggle that creates a riveting tale. If Frodo had waltzed his way to Mordor, knocking down Nazgul left and right without even breaking into a sweat, his victory would’ve felt flat. If it was obvious that Katniss was the only one who could possibly win the Hunger Games, why would we need to finish the story?
It’s the struggle itself that interests readers, and by making your characters too awesome, you rob their triumphs of meaning.
So, break it up. Let your character be wrong sometimes. Have them make mistakes, experience consequences, and deserve them. Have them regret something that was a true moral failure. Allow them to know real defeat. It will make their subsequent victory that much the sweeter.
A writer friend introduced me to this Mary Sue Test, and I’m going to pass it on to you. I think it’s an excellent tool to help you think deeply about your character. It’s okay to have some Mary Sue traits. But don’t forget to give them some human weaknesses, too. Your readers will actually enjoy reading about them more if you do.