Lucas Moura said Tottenham were "too passive" in the loss to Southampton on Wednesday.
Spurs went ahead 2-1 with two minutes remaining but eventually lost the game 3-2.
"No one expected this," Moura told the club's website.
"It was a good opportunity for us. Two games at home and when you have two games at home you need to think about six points and today was not out best game.
"We didn't play well. We were too passive. Too much space for them and they played really well."
The Brazilian added: "We could score two goals, to be one goal up twice during the game but that's [the] Premier League, you cannot sleep [for] even one second.
"They score two goals in [two] minutes, it cannot happen. [We] need to learn. It's a bad day for us.
"Even when you're in a bad day you need to compete. You need to have attitude. You need to work and I think we did," he said.
"We worked well, even if it was not our best day technically, tactically. We worked and could score two goals but we need to know how to keep the result and we didn't."
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