Humans learn by realitivity so and since we are seeing through the lens of ourselves. Everything has the potential to trigger a memory.
It depends on perspective. Some people are more negative as a rule. Others are going through a hard time and in reference to now it seems more idyllic.
Others are highly dwpendent on routine and hate change because it makes them feel like a security has been breached.
Then age comes into factor. Around 27 or 28 a certain part of our brains closes off that deals with personality. Our personality is pretty much set. You can continue to change surface things. But unless something major occurs the core of who you are is already developed.
Change is harder and harder from that point on. The elderly for example each time they go through a move or major shift in routine are apt to loose 5%-10% of their general health.
By that time their quality of life has diminished. So with that in mind looking back and seeing a bed of roses is understandable. Its too bad the rest of us can’t look back and tell whether it is pure sentimentality or mostly truth.
Life and the world is under a constant state of change. There will always be loses with the gains. It is too bad we are too short lived and emotional and too small picture oriented to tell what shifts were for the best.
But then perhaps not because then we can live in peace and not feel the weight of the world. Change is good. Our species will continue until it doesn’t. And not changing is the best way to start that decline.