Iker Muniain scored in the second half as Bilbao inflicted a first league defeat on Barca this season, but Valverde has called on his side to "seize the moment".
"Being well ranked is not anecdotal because it shows that we are on the right track, but it is not much more significant than that," Valverde told reporters at a press conference. "Today's victory gives us confidence for how it was achieved, for the opponent we faced and what we suffered. Let's enjoy this and see if we can seize the moment.
"There have been moments, especially in the first half, in which we were not well, because Barcelona pressed well and had gotten beyond our back-line."
"Physical preparation has relative importance. What I value is the psychological element, which is what drives you many times. A team which always has high intensity never decays."
The result moved Bilbao into fourth spot in La Liga.