The human body has seven chakras, each corresponding with a different characteristic or type of energy. The trick is, if one of them is blocked or clogged, it can inhibit the abilities of the other chakras, especially those that are higher up on the totem pole. A blockage could make it more difficult to practice magick.
In short, making sure all of your chakras are open and free of metaphorical cobwebs definitely helps with whatever you're trying to do, be it a magick based or in your day to day life.
That's one way to think of it. Another is to imagine a hose with water running through it. If you pinch up the hose at one point, then the flow of water to the rest of it is significantly decreased. It may not stop altogether, but it isn't working at optimal conditions.