What advice does the poet give, beginning in line 73, concerning the wisest attitude toward death?

Even though your question is missing the name of the poem, after looking it up, I've found it refers to "Thanatopsis" by William Cullen Bryant.

The poet advises the audience to accept death calmly.

Explanation:

The general tone of the poem "Thanatopsis" by William Cullen Bryant is quite somber. At first calling death "the last bitter hour", the speaker, from line 73 on, changes the mood suddenly. He advises readers to accept death calmly, even gladly, after having lived fully. Death is described as a trip, a journey to an unknown place, a "mysterious realm", where we are supposed to wrap ourselves in our blankets and go to sleep. And it won't be a boring, empty sleep, but one filled with dreams. The speaker tells us to not act as if we were being forced into death, but as if we were willingly approaching it with trust.

So live, that when thy summons comes to join    

The innumerable caravan, which moves    

To that mysterious realm, where each shall take    

His chamber in the silent halls of death,    

Thou go not, like the quarry-slave at night,    

Scourged to his dungeon, but, sustained and soothed    

By an unfaltering trust, approach thy grave,    

Like one who wraps the drapery of his couch    

About him, and lies down to pleasant dreams.