In the Western Hermetic Qabalah (which is not to be confused with and bears little resemblance to the Qabalah of the Rabbis) the eighth sephirah Hod is the house of Mercury and reason. Cups are connected to instinct and emotion, so it's not suprising they find the 8th house an uncomfortable fit. Wherever it turns up it points to a problem which must be addressed and a growth opportunity which the querent has been neglecting.
Like the 8 of Swords the 8 of Cups typically points to background issues rather than spectacular problems. Crowley called it "Indolence" and it frequently manifests as the slacker's card, a clean well-lighted rut which is comfortable but unsatisfying. That Mercurial reason will not be denied: no matter how much the querent tries he cannot shake nagging discontent. In these instances the 8 of Cups must always be answered by the actions indicated in the surrounding cards. Hesitation is not a virtue and soon will no longer be an option.
The 8 of Cups can also point to another conflict inherent within the meeting of mind and heart -- emotional indecision. Frequently the querent is juggling several indulgences, all of which give pleasure but none of which ignite passion. "Follow your heart" sounds wonderful until your heart is confused. When that happens it can be easier to go through the motions and ignore that nagging discontent. The 8 of Cups brings those problems to the foreground, and reminds us that every journey toward a goal starts with turning away from another.
There’s a feeling of world-weariness to this card, a feeling that you’re whiling away your time with idle amusements because you see nothing better to do. There’s also a tinge of bitterness to the 8 of Cups: it’s a retired knight who wonders if there ever was a damn Grail. Left unchecked this can become a façade. Within every cynic beats the heart of a disappointed romantic and nihilism can be more comfortable (and certainly more fashionable) than faith. But it can also be the impetus for a new quest: doubt can paralyze you or it can set you free.
The wall between rationality and emotion may seem insurmountable: as the French philosopher Blaise Pascal famously put it, "Le cœur a ses raisons, que la raison ne connaît point" (The heart has reasons which reason cannot understand"). But remember that the Great Work involves transcending duality. Pascal went on further to explain "We know truth not only by reason but also by the heart." The 8 of Cups suggests the querent is favoring one at the other's expense. Its context in the reading may suggest which is being overlooked, while surrounding cards will offer suggestions on how to break the impasse.