Let me not to the marriage of true minds
Admit impediments."
Do not let obstacles stand in the way of true lovers.
"Love is not love Which alters when it alteration finds,"
Love is not love when change makes the relationship change
"Or bends with the remover to remove:"
Or goes with the obstacle (ie a mistress) and leaves (this line is actually a reference to the dark haired mistress mentioned in other sonnets).
"O no! it is an ever-fixed mark"
It is inevitable (a reference to how love can be a downfall to honourable men)
"That looks on tempests and is never shaken;"
True love can go through storms and survive
"It is the star to every wandering bark,"
It guides the way (like a using stars to navigate ships)
"Whose worth's unknown, although his height be taken."
No one knows what love is, though they take it all and fall in love despite the risks
" Love's not Time's fool, though rosy lips and cheeks "
Love is eternal, it doesn't die, though mistresses come (only whores wore makeup to get rosy cheeks in middle ages)
|"Within his bending sickle's compass come: "
Time sends the whores as part of his twisted (bending) plan
"Love alters not with his brief hours and weeks,"
Love doesn't change over time.
" But bears it out even to the edge of doom."
But stays the same right til the end of time
"If this be error and upon me proved, "
If I bewrong and you love me not
"I never writ, nor no man ever loved."
Than I'm not a playwright, and I never loved.