Feeling left out, sometimes, if not most of the time, makes you feel alienated; alienated from where you belong, who you belong to, the group you hang out with and much more. Sometimes, they make you feel excluded without taking it into account. And you think you don't deserve it, or that maybe they missed including you, but it happens so often, you begin to wonder if your presence as a person really matters.
At home, we may feel excluded by our parents and siblings, and this usually leads us to look for a place where you belong, where you are appreciated and where you are given support, understanding and allowed to give a valid opinion or at least, where you are allowed to speak up. That is where the best friends come in. Brothers and sisters that we choose, that life presents to us and shows us that like us, they are looking for something similar.
And then, there comes a dilemma, you can't have more than one best friend. You will always go to one first before the other, and when this happens, it just means that your trust and judgment will depend more on one person than the other. And no matter how hard you try to avoid it, the other party will feel left out, their opinion won't matter as much as someone else's, and even though the affection is equally powerful, there will always be a greater affection that will go to someone else.
And we will feel bad, and others will not know what is happening, and they will think that it has nothing to do with them, but in reality, the search for the truth will be insignificant, because out of sight, out of mind. It applies to everyone, even if it is a resounding cliché.