Another portal into the Unmanifested is created thought the cessation of thinking. This can start with a very simple thing, such as taking one conscious breath or looking, in a state of intense alertness, at a flower, so that there is no mental commentary running at the same time. There are many ways to create a gap in the incessant stream of thought. This is what meditation is all about. Thought is part of the realm of the manifested. Continuous mind activity keeps your imprisoned in the world of form and become an opaque screen that prevents you from becoming conscious of the Unmanifested, conscious of the formless and timeless God-essence in yourself and in all things and all creatures. When you are intensely present, you don’t need to be concerned about the cessation of thinking, of course, because the mind then stops automatically.
Surrender – the letting go of mental emotional resistance to what is, also become a portal into the Unmanifested. The reason for this is simple : inner resistance cuts you off from other people, from yourself, from the world around you. It strengthens the feeling of separateness in which the ego depends for its survival. The stronger the feeling of separateness, the more you are bound to the manifested, to the world of separate forms. The more you are bound to the world of form, the harder and more impenetrable your form identity becomes. The portal is closed, and you are cut from the inner dimension of depth. In the state of surrender, your form identity softens and becomes somewhat “transparent”, as it were, so the Unmanifested can shine through you.
Reference : The Power of Now. Eckhart Tolle.