The Blaugrana were stunned in Italy, giving up a 4-1 first-leg lead to crash out on away goals, having been favourites for the competition.
Barca have been widely criticised for their display but still lead LaLiga and Valverde says his side must move on quickly, with a tough test against Valencia to come on Saturday.
"We lost the possibility of staying in a competition we were excited about being in – it's a big disappointment," he said.
"It's not just for us, but also for the fans. We feel responsible for letting them down. What you really want is to get back to playing, to put things behind us. We've still got two trophies we can win this season.
"It doesn't matter how many times we look back at the game on Tuesday, it's always a defeat. On Wednesday, we had still lost on Tuesday. On Thursday, we had still lost on Tuesday.
"We can't keep looking back at games in the past. We can't dwell on it. We lost. We need to re-engage with the fans and achieve the challenges we have ahead. It's important to keep focused."
And Valverde now wants a reaction at home to Valencia, harking back to a pair of Supercopa de Espana reverses at the hands of Real Madrid back in August as inspiration for how to recover.
"I would like the reaction to be positive," he said.
"It was the same as with the Supercopa at the start of the season – for three days it looked like the world had ended. It was a catastrophe. We got over things and now it's the same."