覆水難收
fù shuǐ nán shōu
Literal translation: Spilt water (覆水, fù shuǐ) is hard (難, nán) to recover (收, shōu)
Actual Meaning: You can’t turn back time
A poor scholar and his wife lived under a mountain. The scholar focused too much on his studies and too little on making a living; academics pride themselves with this lifestyle, after all. However, the wife was no academic. “Why don’t you go get a real job?” The scholar replied: “My dear - just bear with me for a few more years. I’ll prove that my Liberal Arts degree was worth it.” Brave words, but the wife acquiesced.
Still, they remained poor with no signs of progress until the wife finally snapped: “You lazy sloth! Go up the mountain and chop some firewood to sell. Do some hard, honest work, for once.” And the scholar did just that.
However, as the scholar came trudging down the mountain laden with firewood, his wife was thinking ahead. The local matchmaker mentioned a hot, single carpenter in the area, and the wife was done enduring her austere lifestyle. As such, the scholar came back to his wife holding up divorce papers. After a few minutes of futile pleading, the wife left for the financially stable (and therefore attractive) carpenter.
Several years later, the scholar was given a job referral while catching up with a college friend. With his stellar academics, the scholar became the governor of his home province. He was rich - filthy rich (think American politicians but twice the bribes - err, lobbyists).
Word spread fast, and the wife quickly realized the error of her ways. While the scholar was on an inspection tour back home, the wife knelt in front of her ex and begged to make amends.
The scholar smiled. He called for a tub of water from his servants, then spilled its contents onto the street. “If you can recover this tub of water representing our lost marriage,” the Scholar smirked, “then I will consider your offer.” And thus the Scholar rode off into the sunset with his consorts, smug from his petty revenge.
TL;DR: Gold-digging wife tries to get back with her rich, nerdy ex-husband, who says “no backies”. Some things are simply irreversible, like burning up one fifth of the Amazon rainforest.