I think those sessions are invaluable in therapists' eyes, not a waste whatsoever!!!!!

Expressing such emotion is often considered cathartic, and even if it doesn't feel that way, it's a sign of great vulnerability. Sharing deep emotion is powerful and some of the best use of therapeutic time I believe.

And silence is not a waste- mindful silence where you're allowed to be yourself, hurt and quiet, in good company- I think that's pretty priceless.