That's not what it means, of course. Internal struggle is when a character has to wrestle with his or her own shortcomings, flaws, and conflicting ideologies. And in most cases, it usually translates into character angst.
And that's fine, I suppose. Our shortcomings are what prevent us from accomplishing our goals. To ignore these shortcomings or overcome them in an instant would be a slap in the face to character development. But is there a better way we can incorporate internal conflict into our stories?
In one of the books I'm reading, the main character sees herself as a weak person who has almost no potential for greatness. From the looks of things, she will probably overcome this and discover her inner strength. And maybe that can be a good story. (I can't say, as I haven't finished the book yet.)
But the internal conflict that I want to read? I want to read about characters who are so flawed that they're the cause of everything that goes wrong in the story. Not one of those "My life is hell, how can I overcome it?" stories. I'm talking about "Oh shit, what the hell did I do?" Stories like Kelley York's Hushed or Donna Tartt's The Secret History. Stories where the main character might not be likeable. I love villain protagonists. (I mean, has anyone seen Death Note?) Or even if the character isn't a villain, I want to see them screw up and then have to deal with their own mistakes. (Locke Lamora, anyone? Not that he's particularly repentant about it...)
One of these days I need to do a post about anti-heroes. Remind me if I forget.