Barca had equalled Real Sociedad's 38-year-old record of 38 games without defeat when they beat Leganes last time out, and they eclipsed it with a nervy win at the Nou Camp on Saturday.
Luis Suarez and Samuel Umtiti scored Barcelona's goals and they held on for victory despite Dani Parejo's late consolation. Speaking in his post-match press conference, Valverde hailed a great day for his team.
"This was a red-letter day for us," said the Barca boss, as quoted by Sky Sports. "It was essential to take this major step forward. To win it we needed heart out there on the pitch and to take the initiative with the ball."
Valverde was also pleased with his players' attitude to bounce back from the 3-0 defeat at Roma which eliminated them from the Champions League on Tuesday, ending their hopes of a treble.
"It was three important points really, for a lot of reasons," said Valverde. "First of all, because of the week we've had. The atmosphere around the club this week has been a bit gloomy and we needed to put the brakes on that.
"It was more important that we picked ourselves up after a difficult week and the players have showed great attitude today and stepped up. We have to look forward now. Obviously we are coming off the back of going out of a competition but we've still got a lot of things to win."
Barca's procession towards the league title continues on Tuesday as they travel to Celta Vigo, before the Copa del Rey final against Sevilla next weekend.