This is quoted from Sinead O'Connor's liner notes to her latest album, "Sean Nos Nua": (italics are my own)

"Many of the songs on this record are stories of enduring and unconditional love, love that can't be quenched by fires or floods. They are the beautifully borne pain of real people, who really existed. They teach that pain can be made into something positive and beautiful when one sings it, and so pain can be healed by singing...

I consider all of these songs magical prayers and therefore not sad songs at all. They are only sad to those who cannot feel the true ghosts of the people who are speaking through the songs."

That's about as good an answer as I've heard.

Cheers,
Michael