Barca became the first team to reach six successive Copa deciders following their 3-0 win against Madrid at the Santiago Bernabeu.
Luis Suarez's brace sealed Wednesday's victory and a 4-1 aggregate triumph for the La Liga champions.
Barca defender Pique revelled in the performance post-match, telling reporters his side have achieved something no-one else will.
"Reaching a sixth final...I don't think what we have achieved is something that will ever happen again in the Copa del Rey," Pique said.
"We've won it a lot in recent years but we want to win it again. It's special to qualify for a final. It's actually been more out of habit than anything else. Turning things around against Levante and Sevilla and then this.
"It was an important win. Madrid were on top in the first half, but we took advantage of the space in the second half to win the game and the tie. It's a great way to reach the final. Winning here and reaching the final is always a cause for happiness."
Barca will be back in action in the Spanish capital on Saturday for another instalment of the Clasico when the league leaders face Madrid in La Liga.
The Catalan giants are nine points clear of third-placed Madrid but Pique wants his team to avoid any complacency.
"We've been lucky to win a lot of games here and by some big margins. But it was a complicated match and they're not that far behind us [in the league]. We can't relax now because it would not bode well for Saturday," he said.
"We're coming through this phase of games – which was really tough [away against Lyon, Sevilla and Madrid twice] – really well. You can't always play well, but we're getting results and we hope to get another good result in the next Clasico."
Often outspoken, Pique was his trademark self following the match as he criticised the Spanish media.
VAR has dominated headlines in LaLiga and Pique offered some advice to the media amid the incarceration of political leaders in Catalonia following 2017's referendum, which was deemed unofficial by Spain.
"If Spanish TV spent more time covering the trial of the political prisoners, which is super unjust, so the people of Spain could see a little more of what's going on, instead of talking about VAR, maybe the country would be doing a little better," he said.