User blog comment:IamJakuhoRaikoben/Chapter 411: Quid Pro Quo, Review./@comment-25111584-20141201135113/@comment-7418318-20141201141138

Natsu (and Wendy too for that matter) always activated Dragon Force through the power of feelings... or to be more precise a combination of anger, protectiveness and desperation. The only difference here is that he didn't get an external boost of magic power.

But with the 3rd gen being able to activate DF at will, this was bound to happen eventually. And if you see it as Natsu's magic comtainer finally growing enough to contain enough magic to into DF without outside help, it doesn't even seem like bullshit.

Though I'm glad it took every last bit of magic to enter DF and deliver this one attack before running out. If he could just switch it on and off at will without repercussions, it'd be too strong for now.