My Take: What is Happiness?
I look at this question a bit differently, perhaps with a more "Eastern" view. A theme, oft repeated in my posts, is the pursuit of balance or harmony in life. This concept can be applied in various ways, e.g., we admire people with both inner and outer beauty and opera singers who can project over a very wide vocal range. Colleges seek out multidimensional applicants such as the scholar-athlete. Additionally, classic polar opposites may be better thought of as interdependent, interconnected, complimentary forces or qualities. This Taoist concept of duality, "together one," is symbolized by yin and yang. There is no darkness without light, bad without good, active without passive. In the same way, happiness is not the absence of unhappiness and vice-versa. Simply, it is not truly possible to be happy without having experienced sadness. They co-exist in all our lives. The contrast is vital to the existence of both. Practically, it is easier to endure suffering knowing that doing so will accentuate times of joy. I have found the vast majority of content people learn how to manage this balance. I think that it is safe to say that for the overwhelming majority, the game of life is hard. Winners are always willing to fight, and when down, fight harder.
"That which does not kill us makes us stronger." - Friedrich Nietzsche