Paul Sturrock admitted his Southend side spent too long sitting on their two-goal lead after watching Plymouth stage a late comeback with two strikes in the final four minutes of a 2-2 draw at Home Park.
Michael Timlin and David Martin both found the net to see the visiting Shrimpers coasting at half-time, but efforts from Nick Chadwick and Alex MacDonald levelled matters in the dying stages.
Sturrock said: "I have played and been involved in hundreds of games like that, where a team is so dominant and all of a sudden decides it is going to happen and then goes to sleep. That is what we did."
He added: "I also want to look on the positive side and we are still in the top three, second, and we will take a point because the aim is to win our home games and pick points up away. If we do that we are going to be promoted."
Southend seized the advantage in the first minute when Timlin charged down home goalkeeper Jake Cole's attempted clearance to score from close range, and the visitors' pressure was further rewarded when Martin crashed in a second in the 34th minute.
Argyle responded with a much brighter start to the second half and clawed a goal back when Chadwick fired home from 20 yards in the 86th minute and then smashed a shot off the woodwork to tee up substitute MacDonald's 88th-minute leveller.
"All of a sudden we decided to play back passes and side passes in really poor conditions and one or two of them just sauntered through the last half-hour of that game thinking it was all over, and we paid the price," said Sturrock.
"I have let them know that. At the end of the day you have got to give credit to Plymouth and at the end there they kept fighting and came battling right through, trying to be positive in their approach.
"If you look at how many corners and set-pieces we forced in the first half we could have probably been 3-0 up when we went in at half-time, but in the second half we just allowed ourselves to come off the pace.
"We allowed ourselves to settle on 2-0 and sit on it and sit on it and sit on it, and you all know what football is like. It will come back at you, especially when you have dropped a couple of gears. The hardest thing is to change up when that happens."