the party [is] over

used to say that a period of happiness, enjoyment, etc. has come to an end and one's life is going to get back to the state it previously was, if not worse

The exact origin of the phrase "the party is over" is not definitively documented, but it is used to signify the end of a period of celebration or enjoyment. It is often employed to communicate a shift from a more carefree or favorable situation to a more serious or challenging one.

The staff hardly worked at all under the old management, but they'll soon find out that the party's over.
After a year of traveling and adventure, it was time to return to a regular work routine; the party was over.
When the stock market crashed, investors realized the party was over, and they had incurred significant losses.
Following a period of economic growth, the country had to address its financial challenges; the party was over.
With the end of summer vacation, the students understood that the party was over, and they had to return to school.