User blog comment:IamJakuhoRaikoben/Chapter 381: Where Demons Live, Review./@comment-24956965-20140418114153/@comment-7418318-20140418150005

At the time she said that, she always got close to losing from running out of magic, rather than being beaten to a bloodly pulp, with the one exception being the Phantom arc. But since she didn't have her keys at the time that can hardly count.

Looking at all those fights, it's easy to see why Lucy would consider her limited reserves of magic power her greatest weaknes, since that was what always got her close to losing.

Just look at the Nirvana arc. Even after being almost killed by Zero, she still got up on her feet again, but if it hadn't been for Gemini to show up, she'd have been unable to destroy the Lacrima. Not because of being physically exhausted, weak, slow or wounded, but because of having used up her entire magic reserve in the fight against Angel.

But leaving that aside, why do you say that Lucy is supposed to be weak, slow and not resilient? At no point in the story is that said, but I can provide quite a few examples out of her fights that show she's none of those things.

Against Byro she showed that she's quite quick and nimble.

Against Zero, Hades, Gajeel, Kain... actually in almost all of her battles she showed that she can take a tremendous amount of damage and still get up.

And she knocked kicked Natsu and Reedus across the entire rooms on more than one occasion and carried Natsu in the Lullaby arc as if it wasn't much of a problem. Usually you'd think a young teenage girl without any visible muscles should really struggle to carry a well-trained boy of seemingly the same age, but she didn't.

So much for "supposed to be" slow, weak and not resilient...