Meme: Valuable Vulnerability

There’s an idea i’ve encountered in a couple essays and posts (not on LW) that being emotionally vulnerable is, counterintuitively, a desirable trait. I think this is usually defined as being in a state where what you observe is liable to create negative emotions in you (or in some definitions, a variety of emotions). I’ve heard several people recommend this meme but i’m still trying to wrap my head around it. Personally i usually aim for more manageable emotional states, and i rarely cultivate this kind of state. On the other hand, its popularity suggests, in my opinion, that it has at least some usefulness.

What do LWers think about this concept? What do you think is the main rationale for this idea, and do you think it is a good policy?