Keeping up with 流行りの言葉 (hayari no kotoba, trending slang) and 流行語 (ryūkōgo, buzz words) is crucial for high schoolers. The last thing a teenager wants is to be called out on 古い (furui, outdated) lingo by their classmates. And if Mom or Dad are using it, that might as well be the sound of the last nail being hammered into the coffin of coolness.
So if you're still saying あげぽよ (age-poyo, feeling excited) and さげぽよ (sage-poyo, feeling disappointed), take note: That ship has sailed.
Let's say you're in a situation where you've just finished a juice-cleanse diet and are about to devour a juicy, calorie-heavy hamburger. Instead of expressing your excitement with age-poyo, use the current hayari no kotoba: 神がかってる (kami gakatteru, "It's so heavenly").