what lessons did ulysses supposed to learn before returning to ithaca?

Perhaps the most profound lesson Odysseus needed to learn in the ten years it took him to return to Ithaca after the Trojan War was humility. Because of his hubris (excessive pride), he angered Poseidon and other immortals; consequently, over the course of a decade he lost every member of his crew while his wife and son suffered at home.
Odysseus also needed to learn the necessary qualities of a leader. Because he repeatedly and needlessly exposed his men to danger for his own self-serving reasons, such as indulging in the song of the Sirens and spending time with Circe and Calypso, they suffered and died. Because he was arrogant and stubborn, he failed to look out for the loyal men who followed him. 
Odysseus also needed to learn to properly value and protect his marriage and family. He eventually tired of his dalliance with Calypso and longed for his home with Penelope and Telemachus.