Are they? To me it seems obvious that if one is seeking those emotions actively, then one will be disappointed or worse if they prove unattainable.
For whatever reason, be it psychological or physiological, it is clear that humans cannot maintain a perpetual high. The serotonin is expended, the stimulant wears off, unhealthy dependencies on emotional states are created. An even keel is worth any number of highs in my opinion. The goal should not be an emotion or a high-water mark, but rather to make progress. Progress is tangible, you can hang your hat on it and be proud of it, and most importantly it's available to you no matter how poor your circumstances or station in life are.
For whatever reason, be it psychological or physiological, it is clear that humans cannot maintain a perpetual high. The serotonin is expended, the stimulant wears off, unhealthy dependencies on emotional states are created. An even keel is worth any number of highs in my opinion. The goal should not be an emotion or a high-water mark, but rather to make progress. Progress is tangible, you can hang your hat on it and be proud of it, and most importantly it's available to you no matter how poor your circumstances or station in life are.