The "fierce anger of the LORD" is not a mood. It is the unstoppable drive of your own imagination to finish what it set out to do. This force will not fall back until the thing intended stands in fact. What feels like harsh pressure is the making-good of a promise buried in you from the start, the plan of your own rebirth working itself out whether the mind consents or not.
What it performs is the second birth, the bringing of the son out of the skull of ordinary man rather than any womb. That intent is hidden in every person, and it is carried through completely; nothing halts it partway. "In the latter days ye shall consider it" means the meaning lands only afterward. Once the birth is felt from within, you look back and see it was your own life delivering you.