The former Arsenal midfielder got his first win as manager last night as goals from Nicolas Pepe and Sokratis Papastathopoulos gave the Gunners a 2-0 victory over Manchester United at the Emirates.
And Luiz appeared to suggest that such a performance was impossible for the team while Unai Emery, sacked at the end of November, was still in charge of the club.
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Luiz told BT Sport: "We did a great first half, it was maturity in the second half. We have to be honest and humble to admit physically we are not ready.
"But where physically you are not there you have to put your hearts in.
"You can't change from zero to 10 in one day, one week, one month - but it is beautiful to see how these kids start to understand their commitment, their behaviours of what they need to do for big things in life and big things in football.

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"In life when you are happy, the results can be totally different. If you sleep happy, you can sleep four hours and better than sleep sad for eight hours.
"If you work with happiness and believe in what you are doing it is totally different.
"Our season isn't there. We started very badly, but things can change and there are still some titles to fight for and some improvements for the future."
Arteta learned his trade working under Pep Guardiola at Manchester City and the Spaniard's high-pressing style was evidenced in the way Arsenal played last night.
Luiz added: "I believe he [Arteta] can improve every player.
"Mikel is a great coach and knows football. He was a great player, he brings things and I believe in his philosophy.
"We are going to do big things in the future, but step by step."
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