The attacking midfielder had mixed emotions after their win over the Liga side as he feels they could have already decided the tie
Goals from Ezequiel Lavezzi and Pastore helped PSG to a 2-0 lead in the first leg of the round of 16 tie, but Adil Rami pegged one back in the closing stages of the game to keep Valencia's chances alive.
"There's no doubt we could have left here with a greater winning margin. Nevertheless, we have to leave feeling some contentment because we got the win, which was what we aimed for, and that's the key conclusion which we'll take away with us," Pastore told Uefa.com.
"To a great extent it all went to plan. We'd planned to stay calm, make sure we controlled the ball and coped with their strengths and then break quickly and effectively on the counterattack.
"We could have scored more, but we gave a good account of ourselves, we won and that's what makes us content. This is the way for us to continue performing if we want to go far – very disciplined and very hungry.
"The return game will be hard, like this, and perhaps we will be missing a couple of guys through suspension, but we just have to go out and perform this well again."
The second leg takes place on March 6.