The Bible says the reason people have such a hard time getting along with each other is very simple: We are all sinners. This doesn't just mean that we do wrong; it also means that we want to do wrong.
You see, sin is like a disease in our souls. Like a bad case of the flu, sin weakens us spiritually and keeps us from doing what we ought to do. Instead, we become self-centered and put ourselves first; as the Bible says, "Everyone looks out for his own interests" (Philippians 2:21). When everyone acts like that, you have conflict.
Jesus put it this way: "For out of the heart come evil thoughts, murder, adultery, sexual immorality, theft, false testimony, slander" (Matthew 15:19). Every sin Jesus mentioned will cause conflict between people. No, we don't like to admit we are this way–but if we're honest, we know we are. We can teach children to be polite and we can pass laws to make people behave–but no matter what we do, it is never enough, because it doesn't deal with our basic problem of sin.
This is why we need Christ, for only He can lift our load of guilt, and only He can change our hearts by His Spirit. Has He done this in your life? The Bible says, "If anyone is in Christ, he is a new creation" (2 Corinthians 5:17). This can be your experience if you will open your heart to Christ today.