The most important thing I can tell you is that God not only wants you to become a better person, but He also wants to help you achieve it.
In other words, you don't have to change your life through your own strength (as you've been trying to do). In fact, you can't change it on your own not completely. But with God's help, you not only can start moving in the right direction, but you can also stay on the right path. The Apostle Paul's experience can become yours: "I can do everything through him who gives me strength" (Philippians 4:13).
How do you begin? First, by a simple act of faith commit your life to Jesus Christ and ask Him to come into your life and He will. When we honestly turn our lives over to Him, He comes to live within us by His Holy Spirit. We are no longer alone! God is with us, and as we follow Him, He begins to transform us from within. The Bible says, "Do not conform any longer to the pattern of this world, but be transformed by the renewing of your mind" (Romans 12:2).
Ask God also to lead you to a church where you can hear God's Word and be surrounded with people who will encourage and help you spiritually. Satan will do all he can to discourage you and pull you down but this won't happen if you build your life on Christ. Make Him the center of your life today.