The Lilywhites boosted their survival hopes with a surprise victory over the Championship leaders with the win moving them two points clear of the drop zone.
"We won't get carried away with it, we've had some good results, but we need to build on that and we need to make sure that we don't do what we have done a couple of times before," said Irvine.
"When we've got out of the bottom three we've dropped straight back into it, but we now have to build on what we have done." 'We knew it would be really difficult before the game and we knew it would be difficult at half-time and obviously we've come through it."