Tottenham head coach Martin Jol accused his side of gifting Arsenal their 5-4 win in the north London derby.
He said: "You can't make errors like we did and win football matches. I have some good feelings about the game but also some horrible feelings as well.
"If you score four goals against Arsenal, or any team, at home you expect to win comfortably.
"Arsenal are dangerous on the counter-attack but we made big errors. You cannot give the ball away at the back."
Jol added: "We have to build on the positive things. We showed everyone we can score goals, but we have to improve our defensive play.
"We cannot give the ball away and concede goals like we did."