Final answer:
The nurse should accept the patient's card of appreciation, as it fosters a positive relationship while being mindful of facility policies.
Step-by-step explanation:
The best action for a nurse when a patient gives a card of appreciation upon discharge is to recognize the patient's thoughtfulness, express appreciation, and accept the card. This response not only acknowledges the patient's gesture but is also in line with promoting a positive nurse-patient relationship. Declining the card could be perceived as a rejection of the patient's gratitude. However, the nurse must be cautious not to violate any specific gift policy of the healthcare facility.