Why did the poet's beloved sighed???

The third stanza suggests that his duty to leave is unstoppable; man’s power is so feeble that good fortune cannot lengthen his life, while bad fortune will shorten it. Indeed, fighting bad fortune only shares one’s strength with it. As the beloved sighs and cries, the lover complains that if he is really within her, she is the one letting him go because he is part of her tears and breath. He asks her not to fear any evil that may befall him while he is gone, and besides, they keep each other alive in their hearts and therefore are never truly parted.