Put simply, 'happiness' is a qualitative state that is meaningless without the context, and therefor the means, by which it attained. It states relation between subject and object: I (subject) have happiness (object) because... (relation to such and such). However there have been no fool proof methods of yet attaining the goodlife for everyone, and that is with no shortage of attempts, either offered in advice or forced by dogma! Aside from the relation of subject to object, there is also something intrinsic to the idea of a state of being arising from a relation to other things -- evaluation. Evaluation is a measure in accordance to goal. If you want to live, you will evaluate food is better than poison. As happiness always seems abject to the fulfillment of desire. Perhaps the case would be a simple one, concerning human beings happiness, if we had relatively few desires that didn't conflict with one another. Unfortunate the case might be that I might both want to go out drinking all night, and at the same time arrive to work the next morning less than drained, I will have to arbitrarily evaluate these projected outcomes to one another. But there is nothing that imposes that I must remain continuous with my evaluation. Though I might value a night drinking on the town with my friends, at the sacrifice of sleep and sobriety next morning, it is no guarantee that I will retain this evaluation the next morning as I hug the toilet vomiting, and call out to work. So we have a few obstacles, we have the contingency of happiness to means (i.e. not self sufficient; desire other than, or upkeep to present being), we have the multiplicity of drives and desires (themselves host to different causal phenomena like chemical reflex, or psychological conditioning) that can and often do compete with one another, and we have a capricious nature of fickle moods that alter the priority of values into different hierarchies.

Now lets look at some of the resolutions. We have asceticism, a complete reluctance to participate in the drives rendered self refuting by the mere fact it replaces desire for things with the desire not to have desire. We have hedonism, the complete indulgence of the drives and passions, that leads to conflicting outcomes (like drinking and going to work) and denigrates a persons capacity for self-control over his destiny. We have all forms of moderates, from types that endorse certain characteristics, and curtail others (Romanticism, Idealism, Rationalism, etc.) which tend to rely on the very relation the subject has to the world in which we wishes to be happy in. If you are somehow inclined to think the passions are more important than ones intellectualism, you might call yourself a Romantic, if the inverse, a rationalist. If you fine happiness in setting and (perhaps) achieving ideas of what a human being should be, you will likely find yourself as an Idealist. The list can go on and on I'm sure, but the thing to keep in mind is that these prescriptions for what is more or less valuable, are contingent to the ends these evaluations are seeking. So someone who wishes to live, you will eat food and drink water, if you want to die, you might drink poison instead. If you wish to live long, you might want to carefully mind your diet, if you want your death from poison to be if varying lengths (slow, quick) you will try different recipes or saturation.

This is an important question, not only because is poses a question of one of the most important concepts and emotions we have, but because these things (evaluation based on perceived ends, based on the knowledge one has to employ in achieving them, in the muddy competition of desires for ends to one another plus the fickle nature of mood) are the very prerequisites to cognition in the first place.