The meaning and origin of the expression: The course of true love never did run smooth

The course of true love never did run smooth

What's the origin of the phrase 'The course of true love never did run smooth'?

This expression derives from Shakespeare's A Midsummer Nights Dream, 1598:

LYSANDER:
Ay me! for aught that I could ever read,
Could ever hear by tale or history,
The course of true love never did run smooth;
But, either it was different in blood.

See also: the List of Proverbs.