In Taoism there’s a famous saying that goes, “The Tao that can be spoken is not the ultimate Tao.” Another way you could say that, although I’ve never seen it translated this way, is, “As soon as you begin to believe in something, then you can no longer see anything else.” The truth you believe in and cling to makes you unavailable to hear anything new.
Holding on to beliefs limits our experience of life. That doesn’t mean that beliefs or ideas or thinking is a problem; the stubborn attitude of having to have things be a particular way, grasping on to our beliefs and thoughts, all these cause the problems. To put it simply, using your belief system this way creates a situation in which you choose to be blind instead of being able to see, to be deaf instead of being able to hear, to be dead rather than alive, asleep rather than awake.
From Awakening Loving-Kindness by Pema Chödrön, pages 70–71