Why does Socrates spend so much effort defining and describing the soul in so much detail in the Phaedrus? He tells us outright, in the dialogue. It is because no man can gain true knowledge from a speech, if the orator does not himself know how his speech is going to guide the soul to its first memory of the unified reality of beauty, found in the divine realm. Dialectic is the way to wisdom, and dialectic can only be achieved through speech.
It seems to me, that the problem of desire has three plausible attitudinal responses: The hedonic approach: there is a never-ending supply of desirable things, and life is best lived by pursuing them all. Want is sated when all desirable things have been had. The goal, then, is pleasure at all times, as an equivalent to happiness. The ascetic / Buddhist approach: the things to be desired are never-ending, which means there will never be a time when all desirable things are had.