Graham Greene's quote reflects on the nature of human relationships and the limitations of understanding. He suggests that time can bring about a sense of revenge, but that seeking revenge often leads to bitterness. Greene argues that true understanding between people, whether spouses or parents and children, is elusive. This perspective highlights the complexity of human emotions and the inevitable misunderstandings we face. Rather than trying to fully comprehend one another, which may be futile, we should accept our differences. He proposes that the concept of God was created as a solution to our need for understanding, presenting a being that can grasp the intricacies of human experience. Ultimately, the quote encourages a mindset of acceptance and freedom from the burden of expectations in relationships.