Connections?why are others on top and others let go of so easily

I have often wondered How we decide who is important to us and who's not. Why we choose to let some people remain in our life's and let others slip away. What makes one person more important then another? I find that we an love so many different people on different levels but what makes us decide how much we love someone or how important they will be in our life's. If you made a list of all the people that you love what would make them rank in the order you listed them? I also find that we are more forgiving of some than of others, what makes it okay for others to be taken back or forgiven more or easier than others? Why do we place a higher standards on others? who are we to expect more form some people than we do of others? Is it a connection in a scientific level of hormones & pheromones, or an emotional connection? How do you decide to like or even love someone? What is it for you that makes a person worthy to hold a place in you life or even your heart? How do we decide who gets to stay & who goes? If person 1 on your list and person 3 on your list do the same awesome thing for you does the line up change in your mind, or what if 1 and 3 both committed the same wrong against you. Is 1 held at a higher level of wrong as 3? Is 3 easier to let go of than 1. What makes forgiveness easier to give to some than others? In the hierarchy of our own little personal worlds what makes one person more important or better than the other and why are we so easy to not give others a second thought?