Analysis of Sonnet 18 - I never gave a lock of hair away

I never gave a lock of hair away
To a man, Dearest, except this to thee,
Which now upon my fingers thoughtfully,
I ring out to the full brown length and say
'Take it.' My day of youth went yesterday;
My hair no longer bounds to my foot's glee,
Nor plant I it from rose or myrtle-tree,
As girls do, any more: it only may
Now shade on two pale cheeks the mark of tears,
Taught drooping from the head that hangs aside
Through sorrow's trick. I thought the funeral-shears
Would take this first, but Love is justified,—
Take it thou,—finding pure, from all those years,
The kiss my mother left here when she died.