@Frustration in Excelsis
The last few posts in that thread seem to redefine it so that “love” is not limited to the romantic; most importantly, the “loses the love of everyone she cares for” clearly refers to Celestia and the other members of the Mane 6. We’ve seen it again and again: Twilight is at her worst any time she feels like the other five aren’t with her or when she’s scared of falling out of favor with Celestia. And we see how badly this can spiral out of control as far back as
Winter Wrap Up, as Twilight’s growing worries about not being able to take part in her friends’ tradition leads to bigger and bigger disasters as the episode goes on, up to the point where she’s so desperate to contribute that she overdoes it in a way that nearly winds up ruining the whole thing.
In the human world, this still seems to generally hold true; those without someone to lean on are in very real danger of coming unhinged. This applies not only to pony immigrants (when everyone’s positive memories of her were erased, Sunset was basically on the verge of a temper tantrum until bonding with Trixie helped her get a grip), but for native humans as well (Gloriosa seems like she was coming unhinged from trying to do everything herself long before there were magic gems throwing gas on that particular fire). It also clearly influences magical transformations, with the risk of negative emotion turning you into a literal monster. (Though come to think of it, that’s not exactly unheard of in Equestria, either.)