I wish I understood myself better, because I'd like to work on my faults and become a better person. For instance, I often get myself into trouble because I don't like people telling me what to do, and when they do, I react and do the opposite (even if they're right). Why am I like this?
You aren’t unique; most people dislike it when they think someone is trying to order them around or run their lives—and they often react and do the opposite, even when it’s unwise or wrong. The Bible says, “The way of a fool seems right to him, but a wise man listens to advice” (Proverbs 12:15).
How can you become a better person? Listen: God wants you to become a better person, and the reason is because He loves you and knows what is best for you. This is why I urge you to turn to Christ and ask Him to come into your life right now. He wants to forgive your sins and transform you from within by changing your heart and mind—and He will, if you will commit your life to Him.
Ask Him to help you know your weak points, and then work on them—with His help. For example, if you have difficulty with certain people who (in your view) are trying to run your life, ask God to help you love them and pray for them. Ask Him also to help you weigh their advice carefully and not just react against it.
In addition, seek out a church where Christ is preached and where you can find Christian friends to help and encourage you. The Bible says, “As iron sharpens iron, so one man sharpens another” (Proverbs 27:17).