He is miserly even with his own grief; he neither knows how to bear (consume) it himself, nor how to share (feed) it with others.

The poet uses the striking metaphor of a miser to capture deep emotional isolation. Just as a stingy person hoards his wealth—neither enjoying it himself nor sharing it with anyone—this person does the same with his grief. He cannot bring himself to confide in others, nor can he fully feel and process his own pain, remaining trapped in a silent, hoarded sorrow.