I love this sonnet by William Shakespeare. It is one of the most romantic pieces of Shakespeare. It is commonly interpreted as the view that true love is unchanging, despite changing circumstances, such as the loss of beauty with old age--or even the loss of the other's affection. In this sense, the sonnet can be seen to be a commentary not only on romantic love, but on unconditional love, which does not depend upon reciprocation for its continuation.
Love Is Not Love Which Alters...
Let me not to the marriage of true minds
Admit impediments, love is not love
Which alters when it alteration finds,
Or bends with the remover to remove.
O no, it is an ever-fixed mark
That looks on tempests and is never shaken;
It is the star to every wand'ring bark,
Whose worth's unknown, although his height be taken.
Love's not Time's fool, though rosy lips and cheeks
Within his bending sickle's compass come,
Love alters not with his brief hours and weeks,
But bears it out even to the edge of doom:
If this be error and upon me proved,
I never writ, nor no man ever loved.