Odisea is a direct cognate of the English word "odyssey", referring to a long, adventurous, and challenging journey. It's a very literary and dramatic word that you don't often find in a pop song.
Daddy Yankee uses it to describe the immense difficulty of a long-distance relationship. He sings that this kind of love "termina siendo una odisea" (ends up being an odyssey), a powerful metaphor for the epic struggle and series of challenges the couple must face to stay together.
Daddy Yankee brings pure danceable drama to the pain of breaking up in "La Despedida". Right from the start, he asks for one last kiss before she leaves with "Antes que te vayas dame un beso" (Before you leave, give me a kiss). Even though the beat makes you want to move, the lyrics obsess over a forced separation. He knows people claim long distance builds trust, but he calls that a total mess: "Que un amor a la distancia fortalece la confianza / Y termina siendo una odisea" (That a long-distance love strengthens trust / And ends up being an odyssey). To him, it is an impossible battle between logic and feelings, and his heart is winning.
He even stages a little internal drama, talking to his reflection for advice: "Hablé con el hombre / Que vi en el espejo" (I spoke with the man / That I saw in the mirror). The mirror gives him the classic cliché: let her fly away, because if she comes back, she is yours, and if not, she never was ("si no vuelve nunca fue tuyo"). It is dramatic and a bit over-the-top, especially when he promises to wait until death ("Hasta la muerte aquí estaré esperando"). Yet, he accepts the reality in the final spoken lines: the farewell happens against their will, but they still have to say goodbye.