יָ֭מַי כְּצֵ֣ל נָט֑וּי וַ֝אֲנִ֗י כָּעֵ֥שֶׂב אִיבָֽשׁ׃
My days are like a lengthening shadow; and I am withered like grass.
Rashi on Psalms
Like a lengthening shadow At eventide, when the shadows lengthen, and when it becomes dark, they are not recognizable, but progressively disappear.