Los Che came from behind to take all three points in Catalonia, with Barcelona suffering their first home defeat of the season.
"In the first half we lacked aggression and in the second half we had it. In the second half we had control and didn't suffer in defence against all of Barca's dangers," he told reporters.
"This win is a very big boost for our soul. For our next games we must use the same dose that gave us confidence to win here."
Valencia currently sit eighth in La Liga.