In this quote by poet William Butler Yeats, he reflects on the idea that excessive sacrifice or enduring hardship can desensitize a person, causing them to lose their empathy and compassion. The metaphor of "making a stone of a heart" conveys the hardening effect that prolonged sacrifices can have on a person's emotional well-being. Yeats suggests that there is a limit to how much sacrifice one can endure before it starts to erode their humanity. This quote serves as a reminder to maintain a balance between selflessness and self-care in order to preserve one's emotional sensitivity and connection to others.