Quotation: from Middlesex

I found this quotation from Middlesex by Jeffrey Eugenides interesting:

"Everyone struggles against dispair, but it always wins in the end. It has to. It's the thing that lets us say good-bye" (524).

The thing that lets us say good-bye. In my mind, it usually takes two parties to say good-bye. Is dispair winning in both parties, just the one leaving (the context of this quotation involved a dying person), or just the one who has to let the leaving one go?

Thoughts? Agree or disagree with the quotation? I'm not sure if I fully understand it, but I found it interesting to think about.