Arsene Wenger knows full well Arsenal will not win anything this season if they continue to fail to deliver when it matters most.
The Gunners looked on course to go top of the Barclays Premier League after they romped into a 2-0 half-time lead over north London rivals Tottenham at Emirates Stadium in Saturday's lunchtime kick-off.
But as Arsenal's focus dropped, Spurs rallied to produce a remarkable fightback to win 3-2 and record their first away win over their old enemy since 1993.
"It is painful, but more because we had an opportunity to go top of the league that we did not take, and a mature team, you want them to do it," said Wenger, with Arsenal now down to third place, two points behind Manchester United who are behind Chelsea only on goal difference.
"That is what hurts the most, because that is what is needed if you want to be successful and win trophies."
Wenger continued: "We delivered quite a good game and created many chances. What is much more difficult to understand is that we lack some basic concentration on facts in the game where you can be punished. When you want to win, that cannot happen."