There are at least two ways of looking at the poem 'Mirror' by Sylvia Plath, as there is a possibility that vanity is not the only interpretation. It is true that many readers will think that a woman who cares only for her appearance is truly vain and shallow. However, the value of self-esteem is now widely held by professionals to be of the greatest importance in influencing the wellbeing of the person. Low self-esteem and a lack of emotional support can lead to serious consequences such as depression, mental health conditions, and even acute self-harm, as in the case of the author herself, who later took her own life. In the poem we see a woman who is only just beginning to fear the honesty of her mirror. The mirror is personified and tells us how objective it is; the later part of the poem describes how the woman responds to that. She turns to other, kinder reflectors, such as the moon, a candle, and a lake, but still she feels very low. the lake cannot understand why she has become even more unhappy. It is because she sees that her younger, prettier self no longer exists. It is as if her young self has drowned in the lake.
It is true that we see disappointment and despair, and the references to drowning and tears underline the mood of loss. We also see it in the 'spectre' of an old woman in the lake, representing the shocking truth. The speaker's response is not one of acceptance and confidence in a future with other rewards. Her utter despair and disappointment at what she feels she is becoming is represented by the scary vision of an ugly old fish, and readers may feel that there is more than just simple vanity going on here. It is a body blow to her whole raison d'etre as she fears she may never reach her potential; time is running out. The message seems to be more about loss of self-esteem and control over her own life than feelings of vanity over looks alone.