Penelope says this to Odysseus just after he has revealed himself to her upon his return to Ithaca. She tests him in order to force him to prove that he really is her husband because she's grown quite wary over the long years he's been gone. So, she orders a servant to make up his bed for him outside of their bedchamber, and this sends Odysseus into a rage. He had made a very special bed in a tree that grew up through their home, made it with his own hands and by his own hard work. Thus, he immediately becomes enraged at the idea that Penelope has done something with their beautiful bed, and he describes it in great detail, confirming that he really is Odysseus. Therefore, when Penelope says that no one has ever matched Odysseus's caution, it is ironic because she has certainly proven herself to be as cautious as he. She explains that he shouldn't get angry with her because she's had to become so wise in order not to be fooled by the deceptions of suitors and other men while Odysseus has been away.