Danny Cowley felt his Colchester side lacked bravery after they conceded late to draw 1-1 with 10-man Accrington Stanley.
The U’s had led from the 40th minute thanks to Noah Chilvers’ fine 25-yard low strike after Riley Harbottle had initially brought the ball forward into his path.
Accrington were then reduced to 10 men in the first minute of the second half when Brad Hills was sent off for lashing out at Tom Hopper near the halfway line.
However, the visitors claimed a point with an 80th-minute equaliser after Harbottle diverted Kelvin Mellor’s cross into his own net.
Colchester boss Cowley said: “Sometimes, the biggest mistake you can make in football is trying not to make a mistake.
“We played with too much fear and, for us, it’s always to find the second goal in these moments.
“We were 1-0 up and were in total control of the game and the opponent goes down to 10 men. Once they go down to 10 men, you just need to find your rhythm with the ball and you need to be brave enough and we weren’t.
“We got what we deserved and we conceded a goal against a team that didn’t have a shot on target.
“It’s our job to try to change the mentality of the group and that’s what we’re working hard to do.
“The hardest to affect in terms of players is probably never technical, tactical – it’s always the mentality. We didn’t show up when the team needed us and that was the truth.”
Colchester were the better team in the first half, with Harbottle, Hopper and John Akinde all going close before the break.
However, Accrington showed character to claim a point, despite Hills’ red card, and that spirit was praised by boss John Coleman.
He said: “We were poor in the first half, I thought it was a poor game. We didn’t offer anything going forward in the first half or nowhere near as much as we should have done.
“It was a controversial goal that they’ve scored. Play is allowed to go on and the referee has obviously missed it.
“The big turning point is the sending-off. I was speaking to John Akinde when he came off and he said it was a yellow at the very, very worst. That’s not me saying that, that’s their centre-forward and he was closer than me, but that’s football.
“It wouldn’t be the first time this season that we get a harsh decision against us and it definitely won’t be the last, so you’ve just got to get on with it.
“I thought we showed terrific spirit and nullified their chances and our keeper has barely made a save.”