Swansea City manager Garry Monk said it was "sickening" that two individual mistakes led to the 2-1 defeat by Tottenham in the Premier League.
Christian Eriksen's late goal inflicted a second home defeat of the season on the Swans, who had dominated the game.
"We lost it more than they won it and I do not know how we did not win it. It is very hard to take," Monk said.
"It is an injustice, but football can be cruel at times and we have to learn from that."
He added: "It is sickening, two individual errors have cost us and we were not clinical enough."
Poor marking allowed Harry Kane to profit from an Eriksen corner to give Mauricio Pochettino's side the lead inside four minutes with a powerful header.
Wilfried Bony brought the hosts level with a stabbed shot before Jazz Richards' careless clearance allowed former Swansea defender Ben Davies to set up Eriksen's decisive drive from 20 yards.
"We could have scored a number of goals and didn't," Monk added.
"The second half was one-way traffic and if it had been a boxing match it would have been called off.
"And when you don't take your chances, there's always the chance that a breakaway or mistake can lead to them getting a goal, which is what happened."
Swansea's defeat was their second successive loss following the previous weekend's 3-1 defeat at West Ham United although Monk was pleased with his side's response.
"The effort and performance level was very good, which is what we demanded after last week," he said.
"We got that, but it's unfortunate that the players weren't rewarded for that effort."