The widely held notion that happiness (or lack thereof) is simply the result of chemical (im)balances is one of the greatest PR victories of the pharmaceutical industry.
I remember an old addict speaking of cocaine as if it was his only true love. Waxed poetical about it, the way we remember our first kiss.
Seems that at least some people are wired this way.
Even if one day you could just squirt the cocktail directly into your receptors or otherwise trick them, there's more to happiness as a part of life than turning yourself into a vegetable, but I digress.