Plato argued against the prevailing Stoic view that happiness (rather than pleasure) was the aim of humanity. After all, when you scratch an itch, it's pleasurable - but is scratching an itch for eternity an example of a fullfilled existence?

Personally, I do seek happiness as an end goal. But there is a method that must be progressed through, and I aim to be happy in that period as well. But aims/goals/methods imply effort, and the sense of an action achieved may indicate happiness. So a "happy pill" is not something I'd personally take, because it makes things too easy. I like doing things the hard way - which probably explains why I'm bankroll building on $1 STTs at the moment.

In short, to be happy, do what YOU want to do, what you think is right (either morally or rationally).

As to whether happiness is a social construct, since I'm coming from something of an individualistic/subjective/rational perspective, I'd argue not, but rather a subjective sense of achievement. But there is an arguement that happiness might be seen in a more objective sense. Ach, don't worry, be happy...