Lancaster eyes Southern Hemisphere job
But he added he was desperate to coach again, ideally with a Southern Hemisphere team.
Lancaster's four years in charge of the national side ended in November after he was effectively sacked, following a World Cup where England became the first host nation to bow out at the group stage thanks to defeats by Wales and Australia.
"You think about it every minute of most days, or every day really," Lancaster told BBC Radio Five.
"A lot of things have happened since then but equally it's still very fresh in my mind.
"It's been a tough six months."
Lancaster's move in bringing in rugby league convert Sam Burgess into his World Cup squad just months after his cross-code switch proved controversial.
That Burgess returned to Australian rugby league giants South Sydney Rabbitohs from Bath soon after the World Cup didn't do him or Lancaster many favours in the eyes of many union pundits.
"I don't think there was any winner in the end," said Lancaster.
"If I'd known he was going to go back to rugby league then my decisions would have been different. But we didn't know that at the time.
"He was a great and positive influence in the group. He worked hard and earned the right in our minds to be in the World Cup squad.
"It's a shame the whole thing played out the way it did."
Lancaster hasn't had a senior job since leaving Twickenham, while England under Australian boss Eddie Jones, their first overseas coach, have since won the Six Nations with a grand slam – both prizes that eluded the 46-year-old Englishman.
– 'Brilliant' Jones -Lancaster said: "You'd want to still be doing the job ultimately but I do feel hopefully it's been passed on in a good shape and with good, talented players coming through and Eddie has done a brilliant job in moulding them and getting the best out of them in the Six Nations."
Lancaster added he was optimistic about England's prospects for the 2019 World Cup after overseeing a difficult "period of transition".
"I would hope with the average age now of about 24, and I think Eddie had 550 caps in his starting team, that's going to be up to 700, 800, 900 with the same group of players by 2019.
"We won't be in the situation whereby we're umming and ahhing about who our 30-man World Cup squad is – it'll be clear and obvious.
"We went through that period of transition and we won't have to go through it again.
"Ireland are having to go through it now, New Zealand are having to go through it, South Africa will have to go through it. I think we're well set now for the next four years."
Meanwhile Lancaster was eager to return to the fray.
"I want to coach again," he said.
"The lure of coaching Super Rugby and wanting to coach in the southern hemisphere is a big one for me.
"You can't create opportunities and you certainly can't create yourself a job but the southern hemisphere would be a tremendous challenge from a personal point of view and it would be a great, great opportunity.
"But we'll see – the Premiership, player development, wherever. I'm open-minded at the moment."
Agence France-Presse
