I am a proud member of the Only-Child Society (heretofore referred to simply as "OCS"). I am certain that you (the general public) have made contact on numerous occasions with members of this highly recognizable group. A high degree of independence and need-to-get-one's-way-ism, and "selfishness" (though this designation is often due to misinterpretation of our disposition by laymen) are some of the most notable characteristics of OCS individuals. Not to expose myself as a celebrity, but...I am actually the poster child for OCS.
I could elaborate on several characteristics I share with my fellow OCS members, however, they are so vast in number that I grow weary at the mere thought of it. So, I shall elaborate on the "selfish" aspect of our group only.
Unless it's the sharing of ideas/resources with colleagues, I do not like to share. It doesn't matter what it is - a toy, a pencil, my notes, my partner's affections....- but what's mine, is mine. If you like it, you should have got one for yourself; leave mine alone.
Why do I have such an aversion to sharing? For starters, people are generally disrespectful of other people's things. They chew on the end of your pencil "unknowingly" and return the saliva covered, half eaten, "writing utensil" back to you with a mere "sorry about that" as a pathetic attempt to rectify the fact that they've reuined a once perfectly prestine, working pencil (an act of blasphemy to the Business-Depot gods really). No. I reject your apology. If I wanted a sample of your enzymatic juices, I would have stuck my finger in your mouth, jerk. You owe me a new pencil. Or they borrow your notes, written on crisp, card-stock Five-Star quality paper and they get returned to you, doggy eared with coffee stains accompanied yet again by a mere "sorry about that." I gave you the gift of knowledge and this is the thanks I get? No. I reject your apology...and I kind of want to stab you in your eye...
Also, I have this derranged belief that once I share something, its value is diminished to me, or conversely my significance to
it is diminished. If multiple people can have the same access to the same item, I feel like there is a diminished sense of preference/significance per individual. I like to hold on to my possessions like they're my treasures - like I'm the special gatekeeper with sole, unlimited access. Does this characterize me as a "selfish" individual? Perhaps. Ultimately, I'm just looking out for myself...it's not a bad idea that you do the same.