Shall I compare thee to a Summer's day?
Thou art more lovely and more temperate:
Rough winds do shake the darling buds of May,
And Summer's lease hath all too short a date:
Sometime too hot the eye of heaven shines,
And often is his gold complexion dimm'd;
And every fair from fair sometime declines
By chance or nature's changing course untrimm'd:
But thy eternal Summer shall not fade,
Nor lose possession of that fair thou owest;
Nor shall Death brag thou wanderest in his shade
By misfortune or accident, or simply in the course of time. 
 The adjective “untrimmed” means un-checked or without human intervention.  But it also may be a nautical term, referring to untrimmed sails on a ship: nature is a ship whose course can’t be corrected.
Sonnet 18