Mr Davis believes he can have an influence on the backbenches
David Davis knew quitting to fight a by-election could harm the Tory Party but he calculated media interest in him would "eclipse" any split stories.
Speaking on BBC Radio 4's Desert Island Discs, the former shadow home secretary said the move took "all of my nerve".
But he could not think of any other way to stop plans to extend terror detention to 42 days "in their tracks".
Mr Davis won the Haltemprice and Howden by-election by a huge majority but effectively ended his frontline career.
The government has since dropped plans to force the amount of time suspects can be held without charge to 42 days through Parliament.
Mr Davis has claimed the decision "vindicated" his resignation but critics say Home Secretary Jacqui Smith was forced to climb down in the face of growing opposition from across the political spectrum - including influential Labour figures.
"I didn't want to do what I ended up doing. I am no saint, no hero," Mr Davis told Desert Island Discs presenter Kirsty Young in a show to be broadcast on Sunday.
"I didn't want particularly to sacrifice the remainder of my career for anything but I couldn't think of any other way to stop this thing in its tracks other than by resigning and making as huge an issue of it as I could."
'It shocked everybody'
Pressed on whether he thought his departure - which came as a surprise to the Conservative leader David Cameron, who was reportedly furious with him - would damage the party, he said: "I did that calculation.
"I spent a whole weekend thinking about this, literally, just non-stop, and, of course, historically, parties that are divided lose support and my view was the public would see this as an important stand and that would eclipse the division story."
He added: "This took all my nerve. I was really scared of this. It took the whole previous weekend for me to really, really decide. You can make an intellectual decision but you have to make an emotional decision and, as you say, it shocked everybody."
He also confessed that the move could have been a mistake, as he may never be able to return to frontline politics.
"This could have been a mistake. You might calculate that somehow or other 42 days would have died anyway or, alternatively I could have done a better job of defeating them if I was home secretary instead of shadow home secretary which, presumably, would have happened in due course but again I did a calculation."
He denied that being a backbencher - even one with a high media profile - was a powerless position.
"Being a backbencher, if you know how to use it, is both powerful and free and that second bit is quite important to me too," said the MP.
He also confessed that he did not do enough preparation for his poorly-received speech to the 2005 Tory Party conference, widely seen as the moment at which he blew his chance of becoming party leader.
"I simply made the mistake of not spending enough time on that speech. There's nobody else to blame but me - I made the mistake and I took the hit and I knew that within 24 hours," he said.
Mr Davis, who entered Parliament in 1987 after a successful business career, also speaks about his tough upbringing with a single mother and step-father, the influence of his trade unionist grandfather and the search for his birth father, who he met for the first time 25 years ago.
His music choices include Dire Straits, Puccinni and Get The Party Started by Pink, a favourite of one of his daughters.
He also selects an obscure protest song, Stealing My Democracy, by Australian folk duo Mundy-Turner, which he said was a source of inspiration when he was making the decision to quit.
His luxury is a "magic wine cellar" and his choice of reading material the complete works of novelist Iain Banks.
Listen to David Davis on Desert Island Discs on BBC Radio 4 at 1115 to 1200 on Sunday, 16 November.