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 think that the variety of emotions definition makes more sense. It's about being open to possibilities, even if some of those possibilities are heartbreaking.

In other words, it is about taking emotional risks. I suppose it would be possible to go through life taking as few risks as possible....but such a life would be stunted in some ways. Risk-taking is not always valuable, but it is sometimes valuable.