This quote by Alfred Lord Tennyson talks to the power of a single day. It recommends that a single day can have a profound influence on a kingdom or realm, either for much better or for even worse. It implies that a single day can be the distinction between success and failure, between life and death, between peace and war. It is a reminder that a single day can have a long lasting effect on the future of a kingdom or realm. It is a warning to rulers and leaders to be mindful of their choices and actions, as they can have significant effects. It is likewise a tip to everyone that our actions and choices can have a long lasting influence on our lives and the lives of those around us. A single day can certainly sink or save a realm.