Looking back I find that I have not yet fully explained why I climbed Everest. It is like answering a question why you breathe. Why do you help your neighbour? Why do you want to do good acts? There is no final answer possible.

     And then there is the fact that Everest is not just a physical climb. The man who has been to the mountain-top becomes conscious in a special manner of his own smallness in this large universe.

     The physical conquest of a mountain is only one part of the achievement. There is more to it than that. It is followed by a sense of fulfilment. There is the satisfaction of a deep urge to rise above one’s surroundings. It is the eternal love for adventure in man. The experience is not merely physical. It is emotional. It is spiritual.
Later, the narrator stated that after reflecting on his response to why he climbed Everest, he realised that he hadn't adequately expressed why he did so. In addition, he believed there would be no answer to such difficult questions. For instance, he responded that asking why he climbed the mountain was similar to asking why people breathe, help their neighbours, or do good things. It was impossible to find answers to these questions. It meant that he had no answer for why he climbed Mount Everest.

The narrator also mentioned that climbing Everest was not a physically demanding task. A person who had reached the peak of a mountain had been more aware of how little their existence was in comparison to the vastness of the universe.  He also believed that spiritual changes occur in parallel with physical changes.
A man on mountain top realises his smallness in the large universe
The narrator also stated that overcoming physical barriers was only one bit of achievement. There was a lot more to it, as the sense of accomplishment, the satisfying urge to rise above the current circumstances. It was the never-ending desire for adventure in a person. So, the experience was not just physical, but emotional and spiritual too. The narrator expressed how one felt when one attained their destination. Arriving at his destination would provide him with a sense of accomplishment, fulfilment, and the strength to overcome his challenges. In other words, the narrator was implying that mental satisfaction was also required while climbing Everest in addition to physical pleasure.
Meanings of the difficult words:
Conscious Aware of and responding to one's surroundings
UniverseThe entire world
AchievementA thing done successfully, typically by effort, courage, or skill
FulfilmentThe achievement of something desired, promised, or predicted
Satisfaction A pleasant feeling that you get when you receive something you wanted
Urge Try earnestly or persistently to persuade someone to do something
Eternal Lasting or existing forever; without end or beginning
Adventure An unusual, exciting, and possibly dangerous activity, such as a trip or experience, or the excitement produced by such an activity
National Council of Educational Research and Training (2008). Honeydew. The Summit Within- H P S Ahluwalia (pp.75-82). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.