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They may just be coming off a huge Nationals victory, but the New Directions' happy times are about to come to an end, at least momentarily, on Glee.

"I started crying by the fourth page," Jenna Ushkowitz says. "I know that we'll see the choir room, but it's definitely going to be a different vibe, a different energy so it's sort of the end of an era."

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Tuesday's graduation episode (9/8c on Fox) will see seniors Rachel, Finn, Kurt, Mercedes, Quinn, Puck, Santana, and Mike bid adieu to New Directions and McKinley High — an emotional situation that was not lost on the stars of the Fox musical series. "We're all really enjoying every single moment of what we're doing because it's not going to be like this again," Cory Monteith says.

In this behind-the-scenes video, the cast talks about their final days together in the choir room, and it's not long before the tears start flowing. "It's very emotional. It's been four years together," Dianna Agron says. "I wouldn't trade it for anything. I mean these are some of my best friends. We've gone through some of the most incredible things together. We've just been on this insane journey... I'll remember this forever." More tissues please!

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Watch the full behind-the-scenes clip below. You might be surprised to see just which members of the cast kept it together and which didn't:

Are you ready to say goodbye to the New Direction seniors?