Immaturity

I'm so tired and sick of people who are in their adulthood, yet act like 15 year old immature teenagers. I can't stand it anymore and I'm starting to despise anyone I meet who is over the age of 30, yet cannot for the life of them get out of the selfish and immature stage of their life. They continue on this way without any disregard for people around them.
One thing that irks me the most are people who take advantage of other people to their own advantage and yet it seems they feel nothing or could care less about the welfare of those they are sucking dry. Then again, those that let them take advantage of them are also at fault.
I was one of those people. Now this burning fire in the pit of my stomach makes me really find this mentality to be such a turn off that I don't really want to have anything to do with those like this.
Maybe anger is starting to replace hurt, but I'm realizing my anger is not unjustified.
Selfish people are one's to avoid. One's that in their lifetime, once they have lost the "support" they keep attaching themselves to, are going to lose the most in their life. They will be left out by themselves and will not know how to take care of themselves or they will be forced to grow up so quickly, their mind will be a whirlwind.
Immaturity and selfishness have to be the worst traits to me right now in my life. When I speak of immaturity, I'm talking about grown adults who still play games like they are 16 and can't face up to anything. They use the "silent treatment" to approach solving a problem.
Hypocrisy goes along with this. Immaturity, selfishness, and hypocrisy seem to all join hand in hand at some point and having to deal with that makes me want to throw my hands in the air and back away from anyone showing signs of these flaws in their personality.
I sound angry, but I'm actually just quite fed up and am exhausted from those like this.
I'm done.