fire-breather
One who is intensely and aggressively passionate and fiercely determined. Likened to a dragon or other beast able to shoot streams of fire from its mouth. The company's new boss proved to be a real fire-breather, and in just a few months she turned a once-middling local business into a national powerhouse.
take a breather
To take a short pause or hiatus (from something). You can go ahead on the hike if you want, I'm going to stop here and take a breather. The senator is taking a breather from his campaign to spend some time with his family.