You are partly right; when God created us He put something of Himself within us -- what the Bible calls our soul or spirit. This sets us apart from every other creature, and gives dignity and sanctity to every human being.
But both the Bible and human experience tell us that something has happened to us -- and that "something" is sin. Evil is real, and evil has invaded our lives; our headlines give witness to this truth every day. A baby or young child doesn't have to be taught how to be selfish; it comes naturally to them. And no one -- even the best person -- measures up to what we know we should be. The Bible puts it bluntly: "There is no one righteous, not even one" (Romans 3:10).
This is why we need Christ, for only He can cleanse us from our sins and bring us back to God. God is holy -- but we are not. God is perfect -- but we are not. Only through Christ can we come back to God, for He took upon Himself the judgment we deserve. He did this because God loves us. The Bible says, "God demonstrates his own love for us in this: While we were still sinners, Christ died for us" (Romans 5:8).
Don't be deceived, but face your own need for God's forgiveness. Then by faith turn to Christ and open your heart and life to Him. Your life will never be the same.