Ronnie Moore said Hartlepool United threw away the points after Carlisle United fought back to win 3-2 at Victoria Park.
Pools led twice after Scott Harrison blasted in a sixth-minute opener and Billy Paynter converted a penalty after Jabo Ibrehre had levelled after the interval.
Paynter’s penalty put Pools back in charge with 20 minutes to go, but the home side could not hold on.
Tom Miller equalised with a cross-cum shot before Ibrehre scored the winner five minutes from time.
“You should never lose when you are leading 2-1 with 20 minutes to go,” said Moore.
“We’re disappointed, no doubt.
“We were too brittle at the back, iIt reminded me of last season when I first came here, us just giving goals away, teams not even having to work for them.
“But when you get in front with the penalty, then you see the game out, you don’t lose the game.
“It’s about being professional.”
Moore felt Miller’s 76th-minute goal which made it 2-2 was the game-changer, describing the wing-back’s goal as “lucky”.
“He hasn’t meant that,” said the Pools boss.
“He’s tried to whip it in and it’s done everyone and ended up going in.”