One term is memento mori.
British Dictionary definitions for memento mori
1. an object, such as a skull, intended to remind people of the inevitability of death
Word Origin...Latin: remember you must die
In the OP's example, a vacation scene (such as the view of a beach, etc.) would remind the OP of the limited time frame of the vacation, and thus could be described as a memento mori. The analogy with death is fitting, since death is the ultimate passing in this world and is also in widespread use as a metaphor to describe other endings (e.g. product death, civil death, etc.)
Another term, though not one normally used as a noun, is sic transit gloria mundi.
Sic transit gloria mundi is a Latin phrase that means "Thus passes the glory of the world." It has been interpreted as "Worldly things are fleeting." The phrase was used in the ritual of papal coronation ceremonies between 1409 (when it was used at the coronation of Alexander V)1 and 1963.
I've never encountered anyone describe anything as a "sic transit gloria mundi" (as opposed to a "memento mori"), but it describes the fleeting nature of power, wealth, health, and other good things.
Given the OP's phraseology, someone could say that they are "feeling sort of 'sic transit gloria mundi'".