When we think less about other people and more about what's in our own best interests, we are said to be "self-centered". This was Satan's sin. In the beginning, God created him beautiful. He was the anointed cherub. But Satan eventually switched his concern from God to self.
Satan was cast out of heaven when iniquity was found in him. Here we read of the change that took place in him and how his separation from God and his "self" rule was initiated:
Isaiah 14:13 &14:
"I will ascend into heaven, I will exalt my throne above the stars of God: I will sit also upon the mount of the congregation, in the sides of the north: I will ascend above the heights of the clouds; I will be like the most High"
Satan didn't care what God would think of his lofty desires. God had ceased being a factor to him. Instead, he now proclaimed what he would accomplish apart from God, his creator. And so, as if by some awesome transformation that God had no part of, Satan now was one with self.
There was no room for God in Satan's habitat of self rule. Those who have felt a slight sympathy for Satan are the ones who give him the most pleasure. Sympathy is the last emotion Satan deserves. He knew the glory and brightness that was and is God, he experienced this firsthand, yet he shunned and scorned it and departed from it for selfish reasons. Satan didn't want the spotlight on the creator. He wanted to be both the spotlight and the one it shone upon.
Man is beloved and cared for by God. Thus, mankind is Satan's sworn enemy. Man has the ability to accept and give God's love. The ultimate achievement I suppose Satan could hope to accomplish in his short time left on earth is to get man to deprive God the rule over his life and to treat other humans as beasts and not like the men they are, created in God's image. In essence, to treat man "inhumanly". Satan wants man to believe that they can be as "god's", that they are capable of "self" rule. That they don't need a savior to rescue them from death, hell and the grave. That they don't need God to direct their steps.
Adolph Hitler treated men as animals.
From the concentration camps to the gas chambers, he saw the job through until he departed this life. Hitler sometimes touted Christianity and spoke fondly of Jesus. The most blatant evil imaginable comes often cloaked or paraded with light. Hitler was one of Satan's most willing ambassadors to have ever walked the earth. He marched to Satan's drumbeat and bathed himself in the darkness of "self". The hatred for mankind, Satan's key feature, found a home in Hitler's heart and power in his hands. But Hitler is only one man. Even though the atrocities he committed were staggering, there are men and women who will never go that far, yet they treat fellow humans as beasts just the same. Whether Satan influences a Hitler or a next door neighbor, the outcome is still disastrous.
From the Garden of Eden to this present time, Satan has sought to bring man low. His chief way is to set up obstacles and stumbling blocks between man and his God. Jesus said, "apart from me, you can do nothing". He meant what he said and Satan knows this as well. Why do you think he pushes "self" rule as he does? Why did he tell Eve if she would eat of the forbidden fruit she would "be as God"? He tempted her to eat so she would sin against God, but also to promote "self-rule" in her and Adam's life. To deceive her to believe in the biggest lie since that time to the present: "You must direct your own steps - take charge of your own life" apart from the one who made you.
As I see it, our lack of knowledge when it comes to Satan has proven to be the key factor in our downfall and rejection of God since the fall of man. We are given insights into Satan's nature from the bible and we would do well if we were to ponder and study those truths. I don't believe it is enough for us to only "know God" our creator, father and friend. We must go on and know our enemy as well. He is the destroyer of men's lives who will not be satisfied until he has taken a vast unknown number of souls with him to his eternal fiery home that he will in the end inhabit for all eternity. Know your enemy - His name is Satan. Don't make his eternity your own.