Why would the goddess Circe give Odysseus advice on how to avoid the dangers he will face?

The Sirens

Odysseus returns to Circe’s island. The goddess reveals his course to him and gives advice on how to avoid the dangers he will face: the Sirens, who lure sailors to their destruction; the Wandering Rocks, sea rocks that destroy even birds in flight; the perils of the sea monster Scylla and, nearby, the whirlpool Charybdis; 62 and the cattle of the sun god, which Tiresias has warned Odysseus not to harm.

As Circe spoke, Dawn mounted her golden throne,

and on the first rays Circe left me, taking

her way like a great goddess up the island.

675 I made straight for the ship, roused up the men

to get aboard and cast off at the stern.

They scrambled to their places by the rowlocks

and all in line dipped oars in the gray sea.

But soon an offshore breeze blew to our liking—

680 a canvas-bellying breeze, a lusty shipmate

sent by the singing nymph with sunbright hair.

So we made fast the braces, and we rested,

letting the wind and steersman work the ship.

The crew being now silent before me, I

685 addressed them, sore at heart:

‘Dear friends,

more than one man, or two, should know those things

Circe foresaw for us and shared with me,

so let me tell her forecast: then we die

with our eyes open, if we are going to die,

690 or know what death we baffle if we can. Sirens

weaving a haunting song over the sea

we are to shun, she said, and their green shore

all sweet with clover; yet she urged that I

alone should listen to their song. Therefore

695 you are to tie me up, tight as a splint,

erect along the mast, lashed to the mast,

and if I shout and beg to be untied,

take more turns of the rope to muffle me.’