Just close your eyes, and imagine yourself by the sea. OK, now imagine that it's stormy and cold. Icy rain pelts down, drenching you to the bone. The only thing you see are crashing waves, and sea-birds who soar away, which is what you wish you could do, too.
And suddenly, you do: you're in a warm feast-hall, surrounded by your friends and relatives. A bard sings a giedd, a poetic song much like the one you're writing, and everyone gathers around him, warming themselves by the fire as they listen. Your lord smiles at you and hands you a gold ring as a reward for your service to him. You embrace and kiss him.
But then you wake up, and you're right back where you started – on the freezing, open ocean, with nothing but the sea-birds and sorrow to hang out with. Except now, it seems so much worse, since the memory of the feast-hall renews your awareness of just how much you've lost. You're not the only one who's lost something, though.
You think of a familiar scene: the bloodied bodies of dead warriors lying by a decaying wall where they made their last stand. Wolves and birds circle them, eager to enjoy the feast war has provided for them. The wind of a winter storm howls, eroding the wall that now has no one left to maintain it against nature's onslaught. These men's lives ended just as quickly as your happy dream of the feast-hall. Now their bodies, and the buildings they constructed, will disappear with the passing of time.
Everything you see in this gloomy world just reaffirms your belief in life's fleeting nature. Being in the feast-hall is nice, but it doesn't last long. Even the building eventually decays, just like dead bodies. And everyone and everything dies, eventually. The setting of "The Wanderer" convinces us of the transience of existence – of the fact that that everything, even what seems the most stable – passes away with time.