Willian insists he was "super excited" to join Arsenal before his happiness nosedived and he was forced to rip up his £20million contract.
The Brazilian, 33, joined the Gunners on a free transfer from Chelsea in August 2020 and signed a lucrative three-year deal which included an enormous signing bonus.
But Willian never adapted to life at the Emirates and found the back of the net just once in 37 appearances for Mikel Arteta's side.
He lasted 12 months before returning to his homeland last summer to rejoin his former academy side Corinthians.
Willian agreed to terminate his contract with Arsenal to seal the move, meaning he essentially gave up wages totalling £20million in a gesture which is said to have left club chiefs flabbergasted.
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The former Shakhtar Donetsk star has opened up on his torrid time in North London in a frank interview with FourFourTwo, admitting his poor form was closely linked to his deep unhappiness.
"Things didn't really go the way we'd all planned," Willian said. "I wasn't happy there, and when you're not happy in a place, it doesn't matter how much you try - you're not going to be able to deliver what people expect of you.
"We had a great project and believed that it would work out, but it didn't, and so I chose to leave and do what was best for me."
Willian has made nine appearances in the Brasileirao - Brazil's top flight - since returning to Corinthians, and he is believed to have taken a 70 per cent pay cut to join the Sao Paolo-based club.
He insists he was "super excited" about the prospect of playing for Arsenal but quickly realised he was not comfortable, prompting him to pursue a way out of his big-money contract.
"There are moments in life when the money isn't so important and you need to focus on what makes you happy; to look for a place where you have some pleasure working," William added.
"That's something I didn't have there (Arsenal), and staying only for the money isn't something I'm capable of doing - there are many other things that come first for me.
"I thought to myself that I couldn't stay just because of a contract - after all, if I did, where would my motivation, my pleasure and my well-being go?
"So that's what I had in mind. Everybody saw what I left behind in order to pursue my happiness again."
Willian's Arsenal exit placed even more emphasis on the club's emerging forwards, who have stepped up to establish themselves as many of the first names on the teamsheet.