The fact is that, as Hume said in The Natural History of Religion, "it is not possible for us, by our most chimerical wishes, to form the idea of a station or situation altogether desirable." The reason is that we desire incompatible things. Even if every other cause of human misery were removed, and even if only a single person were in question, that person's desires, being inconsistent, would still be incapable of satisfaction. Remold this sorry scheme of things exactly to your heart's desires: then even if, by some miracle, those desires were compatible with one another, you would sooner or later be bored with the result. In other words, the universal human hankering for novelty would, at some stage, intervene and unsettle all.
From flagamuffin's post. This hits home.