How does Marguerite de Navarre use imagery in The Heptameron?

Imagery:

"'I think that was the hardest thing for her to bear,' said Longarine, 'for when a couple are completely united in love, no burden is so heavy that it cannot be carried with a cheerful heart; but when one of them fails to meet the demands of duty and leaves the full burden to be borne by the other, the weight is beyond endurance'"