Dawn theory of jealousy:

People in our lives are categorize into different groups, these categories are stacked upon each other in the shape of a pyramid. The least important forms the base of the pyramid, while the most important people in our lives are in the tip of the pyramid. Acquaintances are at the base, those that we say hi - bye to , they are the least important people in our lives for which we can conveniently do without. Immediate family and spouses hold the key position. SO ..where do girlfriends and ex-s stand?? I ll assume it is the next most important position in a men's life.. Being in the same category so many others who had once played your role results in jealousy, malicious competition to try to stand out and be different from the previous one, just as how in an audition, participants try to out win the other competitors, girl feel the need to justify themselves to establish a strong hold in their lover's heart. This is an innate human reflection.

Augustine theory of circle:

Our lives are like huge empty drawing blocks, every person who walks into your life leaves a circle, the diameter of the circle is determined by how much you value this person in your life. The more important he/she is the bigger the circle. However, the catch is, the size of the circle may vary. It may grow bigger as someone is promoted from the role of a friend to a girlfriend. While demerits may reduce the size of the circle (lack of confidence, cheating.etc)