Career-threatening calf problems have shackled Flannery to the treatment table for a year, restricting him to only two aborted appearances for Munster last season.
The slow and arduous rehabilitation process took its toll on Flannery's psyche, but disillusionment has since been replaced by cautious optimism.
Three final-quarter cameos for Ireland this month have passed without mishap and his name will be among those read out when the final 30-strong World Cup party is announced tomorrow lunchtime.
Now that the unhappiest spell of his career is over, the 32-year-old hooker is determined to make an impact in New Zealand.
"The last four weeks have been brilliant, even just running around the training field," he said.
"I had a painful time on my own on the sideline watching all of the lads training. It was breaking me mentally.
"I've worked as hard as I can and for so long. The medical team and (coach) Declan Kidney have shown a huge amount of patience and I want to repay them.
"I want to play as much as I can and if I try to take a positive on the last year, whatever's been wrong with my calf the rest of my body is pretty fresh.
"I feel mentally fresh and my hunger for the game has never been so great.
"I don't want to get fit just to make up the numbers, I want to go out there to do something. I want to play hard and win."
The fear of breaking down once again continues to pursue Flannery, but his outlook on his fitness has changed.
"I have a good perspective on injuries now - I don't worry about them any more," he said.
"I don't worry about the injury now at any stage. It's got to the point that if it happens, it happens and there's nothing I can do about it.
"I'm still cautious in managing my workload during the week but on the pitch, it's full on."
While Flannery has been heartened by his comeback, Ireland's problems on the pitch has left him frustrated.
The final scoreline of yesterday's 26-22 defeat by France at Aviva Stadium - their third successive loss - failed to demonstrate Les Bleus' overwhelming superiority.
A bright start from Ireland topped by Cian Healy's try saw them race 8-0 ahead before an alarming loss of composure allowed France to score 26 unanswered points.
Error-prone, indisciplined and rudderless, they produced a confidence-sapping performance that will be of grave concern to Kidney and his coaching team.
Even during their dominant opening quarter - forget the late rally as the game had already been lost - their desire to put width on the ball at every opportunity pointed to tactical naivety.
England complete their pre-World Cup schedule when they visit Dublin on Saturday and Flannery accepts the match has now assumed greater significance.
"Last weekend in Bordeaux we were pleased that we finished strongly against France," he said.
"Things seemed to be coming right and we thought 'we'll apply it to next week'.
"But we can't keep saying next week, next week. It's professional rugby and we're judged on results.
"You have to get it right sooner or later. We were too sloppy for periods and the French exploited that.
"The result against England was always going to be important, regardless of what happened yesterday. It was always going to be huge.
"But for us things have been heightened a little bit because we've had three losses on the bounce.
"We're trying to go into the World Cup in a good frame of mind and that will be based on victory."
Flannery insists Ireland - who posses the Heineken Cup champions in Leinster, the Magners League champions in Munster and a squad full of talent - should be in a better position.
"When I was in the depths last year I looked at the Ireland side, watching them in the Six Nations and seeing Leinster go so well, he said.
"I thought we have so many quality players and such depth that it would just be a case of getting it right.
"That's the frustrating thing - we've lost three games on the trot but the players are there.
"When you lose, that cloud follows you around and it's a pain in the arse."
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