The original question had to be edited. The word choice in the poem talks about how maturation causes youthful joys to be replaced by the passage of time. The images in the second stanza help to bring this condition out into full view:
For the sword outwears its sheath/ And the soul wears out the breast/ And the heart must pause to breathe/ And love itself have rest.
The word choice in this stanza talks about how life passes on and things "get old." The sword outwearing its sheath and the soul wearing out the breast are representative of how the passage of time causes priorities to change. The need for the heart to pause to breath and love finding rest are all examples of how things that once defined meaning and possessed purpose no longer are seen in the same light.
The word choice in this stanza helps to communicate to a modern audience behavior seen today. The notion of "moving on" is a part of maturation. The things that defined one's being are not always the same in both presence and ferocity. People get tired of what is there and part of the mutability in human consciousness is th need to change priorities and preferences. This becomes part of what Byron addresses in terms of people maturing and becoming older. There is a melancholy in the poem which can connect to modern behavior and the "loss of innocence," but what Byron expresses is intrinsic to the behavior of the present times were people simply decide to "move on" when conditions have lost their allure.