Nostalgia is past in the present.

It’s the cool brush of wind against your cheeks, 

The soft flow of cold river water against your legs,

And the rustling of trees during summer.

It could be the most enjoyable when used in the proper amount, place, and time.

It could be a wonderful sensation - The happy memories flowing back to you, reminding you of joy and contentment

It could, however, destroy mankind and sink them into deep, dark, and atrocious thought of misery

But when used in the proper place, it could act as a friend, something nor fluid nor solid that cheers your soul

So beware, and behold