Yes, he was saying that adults must become like children as far as humility is concerned.
What is it that makes children lose their humility as they proceed toward adulthood?
I think William Wordsworth said it best
Our birth is but a sleep and a forgetting:
The Soul that rises with us, our life's Star, 60
Hath had elsewhere its setting,
And cometh from afar:
Not in entire forgetfulness,
And not in utter nakedness,
But trailing clouds of glory do we come 65
From God, who is our home:
Heaven lies about us in our infancy!
Shades of the prison-house begin to close
Upon the growing Boy,
But he beholds the light, and whence it flows, 70
He sees it in his joy;
The Youth, who daily farther from the east
Must travel, still is Nature's priest,
And by the vision splendid
Is on his way attended; 75
At length the Man perceives it die away,
And fade into the light of common day.
Earth fills her lap with pleasures of her own;
Yearnings she hath in her own natural kind,
And, even with something of a mother's mind, 80
And no unworthy aim,
The homely nurse doth all she can
To make her foster-child, her Inmate Man,
Forget the glories he hath known,
And that imperial palace whence he came.
. . .
Thou little Child, yet glorious in the might
Of heaven-born freedom on thy being's height,
Why with such earnest pains dost thou provoke
The years to bring the inevitable yoke,
Thus blindly with thy blessedness at strife? 130
Full soon thy soul shall have her earthly freight,
And custom lie upon thee with a weight,
Heavy as frost, and deep almost as life!