"...And summer's lease hath all too short a date."
As someone has already mentioned, sonnet #18 is probably Shakespeare's most famous and of the ones we read it is, to me, his most interesting. Though I do not have a great deal of experience with Shakespeare, it is quite easy for me the see the universal truth expressed in the third and fourth lines: "Rough winds do shake the darling buds of May, and summer's lease hath all too short a date." As has already been pointed out, these lines most likely refer to a particular lover. But I like to think of them as being more ubiquitous in nature. All good things must end. Summer could represent love, as is the case of Romeo and Juliet, but it could also just as easily stand as innocence, happiness, or even life.