The worst thing you could do would be to assume you can never change, but will spend the rest of your life getting into trouble (even if you don't want to). God doesn't want this to happen to you, and He has the power to change anyone who turns to Him–including you.
And that is the key: to seek God's help for the changes you need to make in your life, and not rely on your own strength. You know you are weak and unable to resist the temptations you face; that's why you are afraid you'll only get in trouble again. The Apostle Paul in the Bible once faced the same problem: "For what I do is not the good I want to do; no, the evil I do not want to do–this I keep on doing" (Romans 7:19).
But this wasn't the whole story for Paul–nor should it be for you. When Paul gave his life to Christ, his life was changed–and the reason is because God came to live within him by the Holy Spirit, and God helped him do what was right. He said, "I can do everything through him who gives me strength" (Philippians 4:13). This can be your experience, as you open your heart to Christ and begin to walk with Him.
God loves you; He loves you so much that He sent His Son into the world to die for you. By a simple prayer of faith ask Christ to come into your life today. Then look to Him every day for the strength you need to turn from sin and live for Him.