nostalgia, n.
1. Acute longing for familiar surroundings, esp. regarded as a medical condition; homesickness.
2. Sentimental longing for or regretful memory of a period of the past, esp. one in an individual's own lifetime; (also) sentimental imagining or evocation of a period of the past.

What the Oxford English Dictionary fails to mention is nostalgia for things that have not yet ended. Premature nostalgia. Perhaps its own medical condition, akin to homesickness, but not quite the same. It has an edge to it, a bite that nostalgia normally lacks. If nostalgia is sepia, then this is overexposed black and white.