This notion is very wrong and can lead us into the realm of unconscious believing. Rather than admitting to ourselves, that we do not know, we try to avoid the discomfort by adopting a belief instead. Reading or hearing something from someone else is still not knowing. Believing what we read or hear is believing, but not knowing.
This may be fine in some areas but is problematic if the benefit of knowing can only be had with true first-hand insight. And avoiding the struggle to know by adopting a belief can leave us without resolving the issue. It may only serve to avoid momentary discomfort and prevent genuine knowing.
A belief is fundamentally the same as not knowing. Realize this! If you say I believe such and such, it would be more helpful to say, I do not know about such and such. What is the purpose of a belief? In most cases, you will find it has no benefit. Just admit that you do not know and go on. Learn to become comfortable with not knowing. What is the benefit of this? Form a mental place of not knowing you at least create the possibility of true knowing. Whereas when you freely adopt beliefs every time you encounter something you do know, it will prevent you from ever discovering what's actually true directly.
In spirituality, this is especially critical, as spiritual insights cannot be transferred through the adoption of a set of beliefs. Spiritual teachings are meant to give you direction for your practice and ways to generate immediate insight, not give you a new world-view to believe in. If you learn that you are one with the universe, the concept itself will not change anything for you, even if you deeply believe it. Admit that you do not know until you do. This way you create the possibility for the truth to reveal itself to you. Beliefs block it.