Reality is gradually apprehended by the quiet mind, and not by the thinking process. Every single spiritual tradition has emphasized the importance of stilling the mind. Easier said than done, but necessary nonetheless.
You can only receive new ideas and energies when the mind is still. The more active you are, the less you are being upgraded. In activity, you are merely repeating what you already know, or perhaps transmitting it to others. In receptivity, you are coming to new understandings. And this is only possible once the mind is still. A thinking mind generates a forcefield, literally, that keeps understandings at bay.
All of those you call teachers or gurus are in a receptive state the vast majority of the time. Their lower minds are not active. They are still and receptive. And they only act when 100% sure about a given activity. They do not act from the place of mindless activity so common to residents of the 3D realm.
While stilling the mind can be done with a formal sitting practice, there are many levels and layers. A short walk in nature can be very beneficial, as can mindfully washing the dishes, making a cup of tea, gardening, or, in truth, a thousand other practices. However, most people do them in order to complete a task/project, which can have the opposite effect. The process has to be given priority over the results. This is a key that has to be continually understood and returned to.
To reiterate - thinking will prevent comprehension, understanding, and realization. The human mind can no more create something than can a calculator. Its purpose is to receive ideas from higher minds and higher sources. It can then execute on these ideas.