Stuart Lancaster will dwell on England's 30-22 defeat by New Zealand in Saturday's QBE International at Twickenham for some time to come.
England reeled in a 17-3 deficit to establish a 22-20 lead, only to be undone by a brilliantly worked try from Julian Savea in the final quarter.
"We're desperately disappointed not to have won," Lancaster told BBC Radio 5 Live's Sportsweek programme.
"It's a case of what might have been and that's what will stick in the throat for the next few months because we don't meet again until the end of January.
"For me as coach that's a long time stewing on it as coach because there was an opportunity there that was missed.
"It's a reflection of where we are as a group that we think we should have won the game and not be happy at keeping it to eight-point defeat."
England's next assignment is their RBS 6 Nations clash with France in Paris on 1 February and Lancaster will spend the intervening time in the company of his family as he reflects on an encouraging autumn.
"The next few days aren't much fun, but my family are pretty good actually. My wife has her own friends and family around her," he said.
"She gets on with her thing and the kids will be back at school. We're a pretty grounded family.
"My mum and dad are from a farm in Cumbria. They'll go back to the farm and do their thing.
"Life doesn't change too much and that's the best way to be because it's about being yourself and doing the best you can."
Lancaster insists the greatest challenge since becoming England's head coach in 2012 is balancing the need to win every match while developing future Test stars.
"The hardest aspect of the job is to win in the here and now and build a team for the future," he said.
"People say to me it's all about winning in the here and now, but I don't think anyone would be happy if I picked a really experienced team that didn't quite have the legs to get to 2015. All roads lead to that and beyond."