Selfish

I've been doing a whole lot of thinking today. How people can be so absurdly selfish, I just don't understand. I'm not talking about a specific individual; I mean in general. How can people be selfish and not feel guilty about it? I admit, I do have moments of which "I" comes before "You" or "Them". But trust me, those are RARE occurrences.
It's true, to survive, you need to put yourself before others. Otherwise you're just being plain foolish. What about when putting yourself first is at the expense of someone who loves you? If not someone dear, someone who is more in need than you are? How do you live with yourself?
I have always been the one who puts others before me. Whether or not you realise it is due to your faulty senses. Point is, I usually try my very best to make sure others are comfortable/ happy/ alright before attending to my own needs. Even more so when it comes to my nearest and dearest. However, I just wonder about those who don't mind taking advantage of their loved ones or friends. Do you know what you are doing or are you in absolute denial?
I guess some people are just so self-absorbed that they forget that there is no "I" in "TEAM" or even "GROUP" for that matter. Maybe somebody should tell them that sometimes it's not JUST about YOU. WE matter too.