"Each issue is torture because the others are gone. Spending sleepless nights summoning the dead, wondering what Charb, Cabu, Honoré, Tignous would have done is exhausting," he said, referring to some of the 12 people killed by Islamist gunmen Chérif and Saïd Kouachi.
He wants to "do some books ... take a bit of time ... reread the Bible, just kidding!" the resolutely secular cartoonist told Libération.
Luz is to publish an album entitled Catharsis on Thursday.
Continuing to work at Charlie Hebdo became "too much to bear", he said but insisted that "I'm no longer Charlie Hebdo but I will always be Charlie" in reference to the #JeSuisCharlie hashtag and posters that spread around the world after the murders.
The resignation has nothing to do with recent tensions in the editorial team, according to Luz.
Franco-Moroccan journalist Zineb El Rhazoui was recently threatened with the sack and 15 out of the 20 staff called for all employees to become equal shareholders.
The current shareholders said Monday that the 4.3 million euros donated to the paper after the killings by 36,000 people in 84 countries, will be "handed over to the victims".
Since the 7 January attack the paper has made a pre-tax profit of 12 million euros, they said, repeating a pledge not to take any dividends and condemning "inopportune declarations, that are inaccurate and a source of ill-intentioned rumours and new tensions".
Cartoonist Tignous - real name Bernard Verlhac - who was killed in the attacks, is to be classified a "victim of terrorism" on his death certificate, the justice ministry has decreed.
His colleague Cabu - real name Jean Cabut - and police officer Franck Brisalaro, who was one of the team's bodyguards, have already been given the same status, which was created in 2012 after Mohamed Merah's murder of Jewish children and serving soldiers in the Toulouse area.
The children of "victims of terrorism" can claim state support, as can the children of war dead.