John Sheridan said Plymouth's dropped points following a 1-1 draw at Accrington could prove costly come the end of the season.
The Pilgrims were on course for all three points after top scorer Reuben Reid had fired home his 19th goal of the season in the 32nd minute.
Victory would have boosted Argyle's play-off chances, but instead they dropped to eighth after Accrington defender Tom Aldred headed home an 81st-minute equaliser.
"I'm really disappointed," said Sherdan. "You go 1-0 up and it's all about seeing the game out, but we couldn't do that.
"We gave them opportunities and half chances and our distribution was poor and it has cost us.
"It's a joke and I'm sick of my players giving the opponents chances to cross the ball.
"It was a brilliant opportunity to get three points and it would have cemented our place in the play-offs - now it could prove costly.
"Reuben might have got his 19th of the season, but he could have had his 20th as well.
"This was a game we should have won, but we have let ourselves down."