Phil Parkinson said he and his Bradford players would "come out fighting together" after a 3-0 defeat at Notts County.
A superb solo effort from Jamal Campbell-Ryce after half an hour was followed by two late goals from Jack Grealish and Callum McGregor as the Magpies secured their first win in four games and extended the Bantams winless run to seven games.
Parkinson said: "It was a very even first half and we had some good moments. But they scored a great goal through a bit of magic from Jamal Campbell-Ryce.
"In the second half, we once again had some good chances and the keeper made some good saves, but we were throwing caution to the wind and got punished with two late goals.
"I've got to take responsibility for that. I left a tired team exposed. But there have been times when I've done that and we've got back into the game.
"We're on a bad run. We haven't had a run like this since I first came into the job.
"We've had some great times, but now we need to take stock, re-assess and make sure we come out ready for our next game to get the three points.
"We've got to come out fighting together, role our sleeves up and make sure we are strong going into the second half of the season."
Campbell-Ryce lifted the Meadow Lane gloom after 32 minutes, taking possession midway inside the Bradford half and passing three defenders before guiding home a precise low strike from the edge of the box.
The game was safe for the home side in the 88th minute when Campbell-Ryce and Grealish combined to release McGregor, who calmly slotted his 12th goal of the season.
Grealish, on-loan from Aston Villa, then profited from Enoch Showunmi's persistence and slid home an injury-time third for County as the Bantams winless run was extended to seven matches.