Carlton Cole's second half header condemned us to a 1-0 defeat and a place in the bottom three of the Premiership.
But that winner came against the run of play after we dominated the first half without reward.
We also started well in the second half but Cole's goal, in the 68th minute, knocked the stuffing out of us.
"I can't change the result - but if I keep getting the same effort from those players the club and the new manager who comes in will have no problems," said acting boss David.
"I'm not low; I'm not low at all. We can see the danger and every club is entitled to be nervous if they're in that position.
"But there are 19 games to go, and it's up to us. If we continue like we played today we'll be okay.
"I thought it was a terrific effort. First half we could have been four goals up, no question. I thought it was a sad result in the end because the lads deserved more.
"We're having a cruel time and have to live with it and fight our way out of it. You have to keep looking forward."
Davis Pleat remained upbeat despite Sunday's defeat against Charlton at the Lane.