Barca secured a 3-0 win in the second leg of their semi-final against El Clasico rivals Real Madrid to win 4-1 on aggregate after two second-half efforts from Luis Suarez and Raphael Varane's own goal.
Real were the better side for long periods at the Bernabeu Stadium as they looked to build on the advantage of their away goal following a 1-1 draw in the first leg.
But Suarez struck against the run of play in the 50th minute and after Varane's own goal had silenced the Bernabeu, the Uruguay striker converted a penalty, Panenka-style, by dinking it down the middle.
"Our form in the cup means that we've been doing really well," Pique said in a post-match interview posted on the club's official Twitter site. "I don't think it will ever be repeated. I don't think any team will get to so many finals.
"We came here and we didn't play our best game of the season and we still won 3-0, so that means something is going right. Coming here recently we've been picking up good results and we're in another final.
"We will try and win this one. We've got the league game here as well and we know that we can't relax because of that."
Barca have won the Copa del Rey for the last four seasons, while the two arch-rivals meet again in LaLiga at the same venue on Saturday.
Real Madrid boss Santiago Solari admitted he found the result hard to take given his side had been on the front foot for extended spells during the second leg.
"After all of our efforts and having fought until the final whistle, having made chances and dominating for so long in the game, this result really hurts," Solari told a press conference.
"We went out with our heads held high but we are not happy about it, we are now focusing our energy on our next clash with Barcelona.
"They showed just how solid they are. We had all those chances and if we had scored them we might have made it to the final."
Vinicius Junior caused Barca plenty of problems with his trickery and pace, but the Brazilian squandered several golden chances, while visiting goalkeeper Marc-Andre ter Stegen made some outstanding saves.
Ter Stegen's best effort denied Sergio Reguilon, whose goalbound second-half header would have hauled Solari's side level on the night.
"We were very good and we were organised," Solari added. "We had a lot of energy and we created a lot of chances, but we didn't score from them.
"Work, organisation, mobility. We had everything and we can add to that what we were lacking - the goals."