Immediately when I gain happiness, I always get the impulsive fear that it will go away. I tried thinking of what exactly to call this — it’s fear, obviously, but it’s the fear of an unknown thing, and seeing as it exists within a realm of happiness, it can’t technically be classified as anxiety.
Anyway, I think that this fear, whatever it is, is the most common malady prevalent in our society — it bespeaks the very malaise which pervades any public place from the bus station, the motor vehicle branch (whereas restaurants are typically more positive), even universities. It’s an entirely ubiquitous flaw, but a flaw nonetheless.