The mind is a really powerful. Everything we believe are results of what our minds tells us. A very remarkable story helps shades more light on this. There was a tale of a very popular figure known as Houdini.
Houdini was a master of escape. He could escape anything he was confined to. No chains or cuffs or cell you put him in could hold him bound. You just give him a couple of minutes and he would break himself out of whatever he was locked in. One day, he was challenged by a king that he could not escape a dungeon of his and Houdini accepted the challenge. The prison guards had Houdini put in one of their cells and left him there with the agree amount of time he requested to break himself free.
After being left alone, Houdini brought out a pin and tried to pick the lock on the door but he wasn't succeeding in this. Several minutes passed, yet, Houdini was still struggling with the door. After the time elapsed, the guards returned back to the cell he had been put in. To Houdini's surprise, the guards opened to cell door without making use of any keys. Turned out that the cell wasn't locked in the first place.
In the mind of Houdini the door was locked and that was why he couldn't open the door even if it wasn't locked in the first place. Whatever our minds tell us, we are most likely to submit to it. That is why the content of our minds is very important. Like a very popular book would say, "As we think, so we are."