On the topic of significant others...that is context overflowing with little daily unselfish acts -- and those are probably even more telling of the natural human capacity for goodness than someone jumping on a grenade to save others.
Sure, there certainly are many. MANY times when I am afraid of my wife and I keep my mouth shut for self-preservation reasons. But there are just as many other times when I'm in the right; when I could say something cutting to her, scratch the righteous itch, get the dopamine rush, and not get any blowback because she knows she screwed up. And I let it go for no other reason than because I love her.