The Ashes-winning all-rounder, who played for St Annes in his early career, beat American heavyweight Richard Dawson on points at the Manchester Arena in November 2012, having been knocked to the canvas during the contest.
Asked by the Sunday Express’s S magazine what was the bravest thing he had ever done, he said: “Sometimes, there’s a fine line between bravery and utter stupidity. The day I decided to climb into a boxing ring for a professional fight was probably on the side of stupidity.”
As for the best day of his life, he cited the experience of being a father.
He said: “I get asked this a lot and people always think I’m going to pick something sporty - playing for England or helping win the Ashes. None of that compares to the joy of being a dad.”
Flintoff, 37, who lives with wife Rachael and their three children, said he was getting rid of his motorcycles.
“I’ve had a couple of motorbikes - a Harley-Davidson and a custom-built chopper. I’m getting rid of them, though. I don’t want my lads playing with bikes.”