Investing in and maintaining friendships is important for deepening and strengthening the relationships. The Risk Regulation Theory suggests that the more we can convey to someone that we won't reject them, the more they can invest in the relationship. Showing affection, being generous, and demonstrating care and consideration towards friends helps to deepen the friendship. Additionally, vulnerability from both parties fosters trust and encourages further vulnerability. The concept of mutuality in friendships involves prioritizing each other's needs in different situations, recognizing that there will be times when one person gives more and times when they receive more. The measure of equality in long-term friendships is seen in the larger scheme of things, rather than expecting constant reciprocity.