Don't Celebrate Just Yet

The party of heroes just defeated the Big Bad. He's finally dead. Hurray! Now we can all go back and live peacefully.... BUT WAIT! During that final encounter with the villain, they completely forgot to deactivate the self-destruct mechanism he activated. It's not that they couldn't, but they just forgot. Cue the Oh Crap moments.

Well, for whatever reason may be, the heroes have survived, but now have somehow been separated during the quest. Friends, Family, or just people that are happy to see each other. When they finally meet back up, they take a moment to celebrate their reunion, but it must be cut short. They are quickly reminded that they have no time to spare to continue on with their goal.

This trope is used to describe when a situation arises when a character or group of characters accomplish something worth celebrating over, but the moment is cut short when someone or something, usually the Only Sane Man, reminds them that they're not out of the woods just yet... Or they just simply forget.

This is mostly a comedy trope, though sometimes played seriously. Sometimes a disaster could be averted if someone had just remembered it.

See also Your Princess Is in Another Castle, for times when it's the audience who realizes that it isn't quite over yet.

As an Ending Trope, Spoilers ahead may be unmarked. Beware.

Examples of Don't Celebrate Just Yet include:

Anime and Manga

In one episode of Pani Poni Dash!, the miserable rabbit Mesoussa has a time bomb placed on him by a adorable and polite "Jinx in Training" who wants him to be unhappy. Becky and a few of her students start trying to figure out how to defuse the bomb over the course of the episode. With less than a minute left before the bomb goes off, Becky arrives just in time to tell Mesoussa that they figured out how to remove it. Mesoussa is overjoyed, everyone starts praising Becky for a job well done, and everyone just starts celebrating at the accomplishment... *BOOM!*
This exact phrase gets thrown around from time to time in numerous battles in Bakugan.

Film

Pulp Fiction: Jules and Vincent have just cleaned out the car into spick-and-span ship-shape, and everything seems hunky-dory when the Wolf reminds them that they still have a dead body to dispose of: "Well, let's not start suckin' each other's dicks quite yet. Phase one is complete, clean the car, which moves us right along to phase two, clean you two."
From Con Air: "Think you're free? Well, think again."
In Star Trek (2009), the crew gets this one and a half times. First, they destroy Nero's ship... but then before they can even think about celebrating, the Enterprise starts getting sucked into the black hole! Once they've freed themselves from THAT unpleasant demise, the Crew doesn't celebrate. Instead, they share a collective sigh of relief. In the commentary, director JJ Abrams said he was trying to avoid having the crew cheer or anything like that. He wanted to avoid "Woo Hoo we kicked ass!" and instead go for "Holy shit did we just do that? I need to catch my breath!"

Live-Action TV

Subverted in the Buffy the Vampire Slayer episode "Fear Itself". The fights over, everybody's back home and stuffing their faces with chocolate when Giles, reading up on the Monster Of The Week they'd just killed, suddenly exclaims,

Giles: Oh, bloody hell, the inscription. I should've translated the inscription.
Buffy: What does it say?
Giles: (referring to the monster which had been dramatically revealed to be a tiny little demon that ended up being squashed by Buffy in two seconds flat) "Actual size."

In the Doctor Who episode "The Doctor Dances", the Doctor was celebrating the fact that everyone lived for once. Rose then reminded him of Jack Harkness, who had taken the bomb that was meant to save them elsewhere. They rescue him too.

Toys

Bionicle: after awakening Mata Nui, the Toa Nuva return to Metru Nui to celebrate, only to find out they were Unwitting Pawns to Makuta, who now took over Mata Nui's body.

Video Games

In Banjo-Kazooie, after you rescue Tootie, the credits roll and there's a cutscene of the victorious Banjo relaxing in a lawn chair—then Tootie comes out and reminds him that he still hasn't defeated the Big Bad, and he'd better get off his butt and do it.
Star Fox 64: "Don't party just yet!"
The intro to Left 4 Dead shows the survivors run from a Witch, fight a zombie horde, deal with special infected, set off a car alarm, and just barely escape from a Tank before they catch a moment's rest on a rooftop.

Louis: We made it! I can't believe we made it!
Bill: Son, we just crossed the street. Let's not throw a party till we're out of the city.

The Legend of Zelda: Ocarina of Time combines this with The Battle Didn't Count; Link storms Ganondorf's Tower, defeats him, and then has to escape the Collapsing Lair with Zelda when the villain tries to pull a Taking You With Me. Afterward, Link and Zelda stand next to the pile of rubble that used to be Ganondorf's fortress, and Zelda begins a post-victory conversation... only for a tremor to shake the area. When Link goes to investigate, a Not Quite Dead Ganondorf emerges from the rubble and transforms into Ganon, the true Final Boss.
In Splatterhouse 2, David's goal is to rescue Jennifer's soul from Hell, which involves storming the eponymous house and opening a portal. However, once he does that, the two aren't in the clear yet, as they still have to escape the house.
Yooka-Laylee and the Impossible Lair; the "impossible lair" refers to The Very Definitely Final Dungeon of the game, which true to its name, is a Platform Hell full of traps. Indeed, the rest of the game consists of Yooka and Laylee (a chameleon and a bat) rescuing the Beetalion soldiers, who each give them a shield to let them avoid damage in the Impossible Lair. Once you get to the end of the place and defeat the boss, however, you then have to escape the Lair before it blows up. Normally, this wouldn't be more difficult, but those shield are likely all used up by then...

Western Animation

In Danny Phantom episode "The Million Dollar Ghost", Jack had just defeated Plasmius (yes, Jack Fenton defeated Plasmius) when he and Danny remembered they still have to change the ecto-filtrator to prevent the Fenton Portal from exploding. Then there was a cut to an explosion scene but it was just Jack showing Danny a simulation of what'd have happened if they failed.
The villain in The Real Ghostbusters episode "Slimer Come Home" (named "Mr. Ugly" by the heroes in-story and "Ghash" in the Storyboards and Script files) is a massive poltergeist who becomes far stronger by absorbing the power of other poltergeists. The heroes manage to subdue and trap him after he combines with dozens of them, but then, as Egon tells them in near panic, the ghost trap now has far more ghosts in it than it was designed to hold, meaning they have to floor it back to the firehouse and transfer them to the containment unit before they break free explosively.