Theory:

     “You hoped,” answered the poet, faintly smiling, “to find in me the likeness of the Great Stone Face. I am not worthy to be its likeness.”
 
     “And why not?” asked Ernest. He pointed to the book. “Are not those thoughts worthy?”

     “You can hear in them the distant voice of a heavenly song. But my life, dear Ernest, has not corresponded with my thoughts. I have had grand dreams, but they have been only dreams. Sometimes I lack faith in my own thoughts. Why, then, pure seeker of the good and true, should you hope to find me in the face of the mountain?”
 
     The poet spoke sadly and his eyes were wet with tears. So, too, were those of Ernest.
Explanation:
 
The poet well-understood the reason behind Ernest's grief. He attempted to comfort Ernest by sharing some truths. To begin with, the poet accepted the reality that he did not resemble the Great Stone Face as he lacked the noble characteristics of it and felt undeserving of it. Ernest, on the other hand, was not convinced. Ernest was moved by the poet's thoughts in his book, and he considered the poet to be similar to The Great Stone Face.  But, he couldn't comprehend the resemblance between the poet's visage and the Great Stone Face. "Are not those thoughts worthy?" he asked the poet, pointing to his book.

As Ernest grew increasingly dissatisfied, the poet began to describe the essence of his poetry, describing them as "heavenly music from afar." As a result, they cannot be a true representation of the poet's ordinary life. There was always a distinction between real and imaginary (dream life).

The poet's views in the poem did not match his reality. The poet confessed to Ernest that he himself has a lack of faith in his thoughts. As a result, the poet felt certain that he did not do justice to the resemblance of such an ageless face (The Great Stone Face). Despite the fact that the poet had a vast number of dreams, they remained just dreams for him. As a result, nothing had actually occurred.
 
The poet also explained Ernest that someone like Ernest, who lives in reality with compassion and honesty, might not be able to notice the likeness of the Great Stone Face in a person like the poet since the poet's thoughts did not correspond with his practical life
 
The poet explained the real facts mentioned above to Ernest in a sad tone, with tears in his eyes. Ernest's eyes were also filled up with tears after listening to the poet's explanation.
 
Meaning of difficult words:
 
S.No
Words
Meaning
1.
WorthyPossessing suitable or deserving qualities
2.
CorrespondConnection or relationship between two or more things
3.
LackA situation of shortage or less thing than expected
4.
SeekerA person who is searching for something
5.
ConfessAdmitting the mistake or wrong thing committed
Reference:
National Council of Educational Research and Training (2008). Honeydew. The Great Stone Face II - Nathaniel Hawthorne (pp. 128-132). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.