A human being has such a potential that he can just about accomplish whatever he sets out to accomplish. There is nothing on this earth that can be denied to you. I want you to believe this. There is nothing on this earth that can be denied to you. You can have it if you know the right mental way to go about accomplishing it. But, you see, there are a few subtle tricks. You have to judge your capacity to concentrate. There is nothing in the world that can be denied to you once you have learned to gauge your capacity to concentrate. And the greatest obstacle in the way of your concentration is the habit of dwelling on your problems. People say, "How am I going solve my problems if I don't think about them?" Constructive thinking is one thing: sitting down, looking at the problem, analyzing it, examining the possibilities, with a clear and neutral mind, a mind without an emotional load concerning the problem. Because it is that emotional load which creates the block.