What does Thoreau advise people to do to ensure their lives are not “frittered away by detail”?
"Simplicity! Simplicity! Simplicity!" Thoreau ponders the state of man in his time who feels that the nation must have a government bulging with bureaucracies--"petty states" as Germany had at the time--commerce, and all kinds of "progress." Satirically, Thoreau asks,
If we do not get out sleepers, and forge rails, and devote days and nights to the work, but go to tinkering upon our lives to improve them, who will build railroads? And if railroads are not built, how shall we get to heaven in season? But if we stay at home and mind our business, who will want railroads? We do not ride on the railroad; it rides upon us.
Thoreau refers to many men who died in the construction of railroads, men whose lives were lost in the name of "progress"; men whose lives were, in fact, wasted in "such a hurry and waste of life."
If a society were to keep itself in "simplicity," people could live more authentic lives and not be slaves to commerce or the development of complications of life in the name of "progress." Men will not have to wake up in the morning with obligations to others; instead, they can live their own lives in a manner in which they do what is meaningful to them and those that love them.
I would say that Thoreau's advice on this topic can be boiled down to the idea that you should keep it simple. He is saying that we have too much going on in our lives (I wonder what he would think of our lives now with TV and iPhones and all of that...) and that we should cut back. We should make our lives simpler so that we do not get bogged down with all the details.
What Thoreau says is that we should cut back. We should not have so many possessions, we should not try to live in such fancy ways. If we would just cut back, we could pay more attention to the things in life that are truly important. Here's a relevant quote:
Instead of three meals a day, if it be necessary eat but one; instead of a hundred dishes, five; and reduce other things in proportion.