Chris Coleman cut a frustrated figure at full time but admitted his players must move on quickly ahead of Tuesday’s trip to Bolton Wanderers.
After a slow start the Black Cats were punished when Kamo Mokotjo and Neal Maupay handed Brentford an assured advantage after 28 minutes.
The Black Cats rallied back through George Honeyman who lashed wide before half-time, with Aiden McGeady and Joel Asoro drawing saves from Daniel Bentley in the Bees goal also.
Josh Maja and Jonny Williams squandered further chances in the second 45, but Dean Smith’s side held firm to leave Wearside with the points as Sunderland remain adrift.
Speaking to safc.com, Coleman provided an honest assessment of the match.
“We have been here before haven’t we,” he said.
“The first 45 again. We are just nervous, and the opposition don’t have to work too hard to score a goal.
“If we look over the course of 90 minutes, there was more action in their last third than there was in ours, but we just never took those chances that came our way.
“They capitalised on theirs. Things are very negative at the moment, it is another defeat, but it is not just that it is the slow starts.
“The nervous starts. We are slashing at passes and knocking the ball out of play when we should be calmer and more composed.
“Then it gets more desperate but how many times have I stood here and said those things?”
He continued: “We have got three days to turn another negative into something positive - it is as simple as that.”