All the angels are amazed at humans, who through their holy works appear clothed with an incredibly beautiful garment. For the angel without the work of the flesh is simply praise; but the humans with their corporeal works are a glorification! Therefore the angels praise humans' work.
An act of love that fails is just as much a part of the divine life as an act of love that succeeds, for love is measured by its own fullness, not by its reception.