The Bantams went down 4-2 at home to Coventry on Tuesday night - a ninth defeat in 11 games that saw them drop to the foot of the League One table.
“I keep saying the same things every week,” conceded the Scot.
“It’s difficult to take.
“You shouldn’t have to be scoring three or four goals at home to get something out of the match.
“I thought we played some of the best football we’ve played since I’ve been here.
“But we don’t take our chances.
“It’s so naive that it’s schoolboy stuff (defending).”
The game was not short of controversy, especially late on when City’s George Miller was sent off.
Miller was handed a second yellow card after the referee deemed he handled the ball into the net.
Hopkin believes that it was a worthy goal, and it would have made the score 4-3 with just a few minutes remaining at that stage.
“George’s sending-off baffles me,” he added.
“He was adamant it came off his chest.
“I was thinking it was 4-3 with six or seven minutes left.”