Brendan Rodgers' side have slipped to 12th in the Premier League table and they were put to the sword by a resurgent Villa who are now unbeaten in five league games.
Prior to the defeat at Anfield, the Reds had won their last three games in all competitions, but Johnson says that they must put it behind them and focus on next weekend's clash with Fulham.
"Any game you lose is disappointing. I think we were lacking a bit of tempo. It was difficult and it was just one of those games," Johnson told the Liverpool Echo.
"It was a great opportunity to pick up three more points and we missed out. We have to put this behind us. It's gone now and there's nothing we can do about it.
"We have a lot of games coming up and we have to look to put things right next weekend."
Johnson thought that Liverpool started the game well and that they were unfortunate to go behind, saying: "Early on we had so much of the ball and dominated the game. They went in front completely against the run of play.
"When we were 1-0 down, we still had a big chance as there was plenty of time left in the game. But the second goal before half-time left us with a lot to do.
"You can say we needed to pass the ball that bit quicker, but sometimes it's difficult to play too quick because you have so much room. When you're in loads of room then you are supposed to move into that space.
"When the opposition are so compact around the edge of the box then your little passes have to be perfect. When you have a day like we did when your passing isn't perfect, that makes it very difficult to break them down."
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