Zeno of Citium believed that love was one of the key aspects of human relationships and it was important in helping us to achieve eudaimonia (fulfillment in life). He believed that love should be guided by reason and virtue, and be based on mutual respect and understanding. He also believed that love should be free from negative emotions such as jealousy and possessiveness, and that it should be a rational choice. Zeno felt that love should be universal, and one should love all fellow human beings as well as oneself. He believed that love should be unconditional and free from any self-interest. He also encouraged us to love our enemies and strive for harmony in our relationships. "Love is a God, who cooperates in securing the safety of the city." — Zeno of Citium (as quoted in Deipnosophists by Athenaeus, xiii. 561c).