Which phrase in the excerpt refers to the restraint that Lincoln wants his audience to show? excerpt from Abraham Lincoln’s First Inaugural Address

I AM LOATH TO CLOSE. We are not enemies, but friends. WE MUST NOT BE ENEMIES. Though passion may have strained it must not break our bonds of affection. THE MYSTIC CHORDS OF MEMORY, stretching from every battlefield and patriot grave to every living heart and hearthstone all over this broad land, will yet swell the chorus of the Union, when again touched, as surely they will be, by THE BETTER ANGELS OF OUR NATURE.
Capitalized=an answer option.