Haki is a power people are using in One Piece to knock people out, to break things, or to fight logia users. Its the fucking Chi of One Piece, how can you say anything to the contray lol? Was Luffy not determined as fuck when Aokiji nearly killed him? Or the first two times against Crocodile? Otherwise, how else can you explain generic amazon women using Haki better than Luffy when he had defeated a Shichibukai? Are they more determined than Luffy? Of course not. Nami is not a Haki user. She can resist it, but that doesn't mean she can use it.