Do you think that nothing ever goes right for you? Do you believe that you are just an unlucky person, and that no matter what you do, you will probably fail? Well, you are right, but not for the reason you think.
Then, in order to make life match up with your belief (which is important for your sanity), you begin to act in ways that reinforce your belief. You may even unconsciously sabotage things, so that you will fail. But you will be acting like you know yourself to be, which is what all of us do. You create what is called a self-fulfilling prophecy.
So if you want to change your life, what you need to do is first change your beliefs. And yes, this is possible. Then, you will continue to act like yourself, but you will see yourself differently, so your behaviour will be different. And when you change your behaviour, you change the results.