The kind of pain and ache that the poet feels is an emotional pain rooted in the realization of her mother's advancing age and approaching death. The poet sees her mother's face as pale and corpse-like, which evokes a deep sense of sorrow, helplessness, and fear of losing her. This pain is not just about physical aging but also a nostalgic and emotional ache that revisits childhood insecurities about separation and loss. The poet regrets not being able to give enough time and care to her mother and is disturbed by the thought of parting from her, which causes both pain and a sense of inevitability at the face of aging and death.