Canterbury completed at over 80% and had slightly the better of possession in their 34-6 loss to the Titans on Monday night but came up with fundamental errors at key times to make life far too easy for their opponents.
Barrett described the performance as "not good".
"I thought we were our own worst enemy again. A lot of ill-disciplined errors and gave them too much footy," he said.
"We put ourselves in a position there, we were on the right ledger with possession, had 50-50 of the footy and I think we only had two incomplete sets in the first half but the two turnovers were at crucial times in good-ball situations."
Jayden Okunbor's fumble off a Titans goal-line drop-out with the Dogs attacking and just 6-0 down was a key moment, according to Barrett.
"The one off a drop out – you just can't (do that). We've got a few blokes in there who need to have a good look at themselves," he said.
Despite his disappointment, Barrett said making much in the way of selection changes was simply not an option with the current depth in the squad.
"There's five or six games to go, we've just got to keep aiming up," he said.
"We've got a thin squad. The individuals we've got, that's what we've got. It's up to them to get better.
"We need to take a lot of pride in what we do in the next month of footy. It's not going to stop."
Barrett said the recent disruption with the game being rescheduled after a snap COVID-enforced lockdown was not a factor in the performance.
"It is what it is, it's the same for everyone," he said.
"The NRL's doing a terrific job. And the Queensland government's been good to allow us to come up here. We'll do whatever we have to do to keep the competition going.
"The players are professional and we expect them to perform no matter what their preparation's like but we had a good prep. It didn't worry us and we've still got a six-day turnaround so no excuses there. They've just got to get their heads around it.
"It's hard for some of the players with young families, we're all in the same boat though. We're professionals and we have to deal with that.
"We need the competition to keep going. There's a lot of people employed within the NRL throughout clubland and the governing body so we need to keep playing, we understand that.
"Players are making a huge sacrifice and a lot of the staff are as well but we understand that we're in a privileged position to be working and there's a lot of other people worse off than us, we'll be ok."