Lionel Messi scored two and made two as Barcelona beat Lyon 5-1 to make the last eight of the Champions League for a 12th successive season.
There was a moment in the second half when Lyon got back to 2-1 and looked capable of an upset for a very short spell.
"We suffered a little bit at 2-1 and to be honest it wasn't necessary," Messi said. "We complicated things for ourselves at a set play because they hadn't done anything.
"Luckily we then got the third goal... There was moment of suspense before [it crossed the line] I thought it wasn't going to go in. But it did and that calmed us down."
Messi's heroics came after Cristiano Ronaldo scored a hat-trick to help Juventus come from behind to beat Atletico Madrid on Tuesday.
"What Cristiano and Juventus did on Tuesday was impressive," Messi added. "It was a big surprise. I thought Atletico would be a lot stronger, but Juve were all over them and Cristiano had a magical night."
Barça are joined in the next round by four English sides, Juve, Ajax and Porto.
"We don't want to choose [an opponent for the next round] because they're all really tough," he said. "[Manchester] City, Juventus, Ajax, who have a great team of kids and don't fear anything, Liverpool, who've shown they pack a punch...
"We're relaxed and we have to prepare for the toughest test possible, which is what's coming now."