For me, controlling my emotions brings a sense of inner calm -- happiness. There is nothing better than thinking with a clear head, without being dogged by feelings of anger, anxiety, jealousy, fear or sadness.
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.
I don't enjoy wild swings of emotion and the loss of control that often accompanies; so level-headed and clear thinking are better for me.