The author creates a tone of regret in the poem "on turning ten". which line best demonstrates the tone of regret?

On Turning Ten is a melancholic and sad poem related to coming of age. The narrator shows his sadness with the lines "the first big number" which he attributes to the age of ten. The melancholy is depicted with the ideas of being a child again and having those wonderful times again. The last stanza of the poem shows the culmination of the pain and difficulty of life:

It seems only yesterday I used to believe

there was nothing under my skin but light.

If you cut me I could shine.

But now when I fall upon the sidewalks of life,

I skin my knees. I bleed.

hjsdhfgfi hfw gf uhwef iwefhuiewg ieufg is aokawfiua