What conflicting emotions does the seafarer feel when he sets off on a sea voyage?
The Anglo-Saxon poem The Seafarer was translated into modern English by S.A.J. Bradley in his book Anglo-Saxon Poetry. The book was published in 1998. The quotes used in this answer will refer to his translation of the poem into modern English. In lines 19-26 of the translation,
Sometimes I would take the song of the swan as my entertainment, the cry of the gannet and the call of the curlew in place of human laughter, the sea-mew's singing in place of the mead-drinking. There storms would pound the rocky cliffs whilst the tern, icy-winged, answered them; very often the sea-eagle would screech, wings dappled with spray. No protective kinsman could comfort the inadequate soul.
the persona of the poem decries his loneliness. In place of human laughter, all he has to accompany him are the peals of birds. In place of warmth, the seafarer has to deal with the harsh waters. When he is at sea, the seafarer is at a place of discomfort.
However, in spite of all his discomfort, the persona of the poem remains drawn toward the sea:
Now, therefore, the thoughts of my heart are in conflict as to whether I for my part should explore the deep currents and the surging of the salty waves—my mind's desire time and time again urges the soul to set out.... (lines 33-36)
In spite of the sea's many threats and dangers, no amount of boons could confine the seafarer to land:
...he will have no thought for the harp, nor for the ring-receiving ceremonial, nor for the pleasure of a woman nor for trust in that which is of the world, nor for anything else, but only for the surging of the waves—and yet he who aspires to the ocean always has the yearning. (lines 43-47)
The seafarer is conflicted because he knows of the sacrifice one has to endure when one is at sea but is nevertheless drawn toward it. He is, at the same time, comfortable and uncomfortable at sea: while he understands the comfort of being on land, he always yearns and aspires for the ocean. He is lonely at sea but also lonely without it.