How does "age" affect the poet's life and what helps him to compare it?

"O Youth! for years so many and sweet 'Tis known that Thou and I were one, I'll think it but a fond conceit - It cannot be that Thou art gone! Thy vesper-bell hath not yet tolled - And thou wert aye a masker bold! What strange disguise hast now put on, To make believe that thou art gone? I see these locks in silvery slips, This drooping gait, this altered size: But Springtide blossoms on thy lips, And tears take sunshine from thine eyes: Life is but Thought: so think I will That Youth and I are housemates still."

In this section, Coleridge speaks of youth's hautiness, that devil may care conceit and attitude that accompanies the time in which we see ourselves as immortal. Age has affected him physically—locks in silvery slips—drooping gait—altered size. None-the-less, at this point in time he still feels young in his mind and soul.