(In the Katha Upanishad) Yama speaks of the unique nature of this journey and its goal:

नायमात्मा प्रवचनेन लभ्यो न मेधया न बहुना श्रुतेन ।

यमेवैष वृणुते तेन लभ्य- स्तस्यैष आत्मा विवृणुते तनूं स्वाम् ।।२३।।

(Nayamatma pravacanena labhyo na medhaya na bahuna srutena; Yamevaiaa vrnute tena labhya stasyaisa atma vivynute tanum svam.) 1. 2. 23

‘This Atman cannot be attained by study of the scriptures, nor by sharp intellect, nor by much hearing; by him is It attained whom It chooses, to him this Atman reveals Its own (true) form.’

The Vedas themselves speak of further steps, besides study and hearing (sravana), for the realisation of the Atman; these are manana, rational understanding, nididhyasana, deep meditation. We need scriptural study which enlightens us with the experiences and teachings of those who have traversed the path to God; we need sharp intelligence to grasp correctly what we study and observe; we need to hear about the Atman and the higher life. But these are not enough; we need to apply our reason to sift what we have gathered from study and hearing; and, finally, we have to concentrate on the truth of the Atman and dwell on it in deep meditation.

Reference: The Message of the Upanishads by Swami Ranganathananda (p.396,397)