What is unhappiness? Your intuition might be that it is simply the opposite of happiness, just as darkness is the absence of light. That is not correct. Happiness and unhappiness are certainly related, but they are not actually opposites.
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And matters are hardly helped by nature’s useful idiots in society, who propagate a popular piece of life-ruining advice: “If it feels good, do it.” Unless you share the same existential goals as protozoa, this is often flat-out wrong.