John Pantsil suffered the misfortune of scoring his third own goal of the season when he inadvertently headed in a centre from Villa winger Stewart Downing, but goals from Andrew Johnson and Clint Dempsey cancelled out the error from Pantsil and Kyle Walker's effort.
Houllier said: "We dropped two points. Had we got a second goal at 1-0 the game would have been over. But we have to be disappointed with ourselves, we have to blame ourselves.
"I'm disappointed with the result but not the performance. At times we played good football and are improving. But we need to be more clinical and ruthless.
"That was also the case when we played Manchester United here. In the final third, we must show more aggression. But it is a long season and we are learning.
"We could also have avoided both goals we conceded. We have enough height at the back. The players were disappointed with themselves but there are positives I can take from the game."
Source: PA
Source: PA