Super sub David Nugent clambered off the bench to sink Sunderland with a stunning late double and keep Burnley's proud 100% home record intact.
Graham Alexander put Burnley ahead from the spot before Darren Bent equalised but Bruce said: "The game was there for us to be won and I was delighted at half-time but it was disappointing that we petered away to nothing in the second half.
"We were the best team by a distance - we let in a poor goal and bounced back from it. The second-half performance is something we have got to put right.
"We knew Burnley would get better in the second half. To be honest we hardly gave them a kick in the first. For the second half, especially the last half-hour, we weren't there."