In Milton’s “Sonnet 19,” the basic message is that one need not pursue one’s hidden talent or engage in activities that make one famous in order to serve God’s will. Instead, as Milton claims, “who best /Bear his mild yoke, they serve him best” (Milton), an attitude which seems well-suited to his Puritan faith and outlooks.
At the start of the poem, the speaker is frustrated with his plight (seemingly blindness and thus inability to use his writing talents), feeling that losing his talent means his death, rendering him useless and unable to serve God. However, he continues that when tempted to tell God exactly how he feels and to ask how God can expect him to perform his labor without sight, his devout inner Puritan self (symbolized by “Patience”) checks this urge, reminding him that his work is superfluous in the great scheme of things. Simply bearing his burden with patience is service enough.
I found the poem rather wordy and somewhat ponderous despite being rather brief; Milton writes densely and, to the modern eye, his use of word order seems awkward. However, it makes a useful case for patience, since one need not be frustrated at one’s inability to follow a calling or exploit one’s talents; it is enough to simply live one’s life, accept one’s circumstances, and bear the load without bitterness. This patient approach to seeking contentment reminds me of some of my older relatives, particularly my maternal grandparents, who were intelligent people but never had the opportunities to pursue and education or live their own lives as freely as they would have chosen. Instead, they did not complain, did the duties that were imposed on them, followed convention (albeit a bit uncomfortably) and accepted the lives they had been given, rather than the lives they wanted to create, and found some degree of fulfillment in that.