Seamus Coleman was visibly disappointed as Poland ended the Republic of Ireland's hopes of automatic qualification for the Euro 2016 finals.
Robert Lewandowski's 15th goal in 447 minutes of football for club and country secured the home side a 2-1 win to end their Group D campaign in second place behind world champions Germany.
Everton full-back Coleman said: "We're all disappointed. After the lads did so brilliantly against Germany we came here full of confidence and it just wasn't meant to be tonight. We've let ourselves down and fair play to Poland, they got there in the end but we've got a big match next month that we have to pick ourselves back up again.
"There were periods throughout the group that we would pick this play-off place, so you have to look at the positives straight away and move on."
Coleman admitted the Republic made a mistake in allowing Bayern Munich forward Lewandowski too much space in the danger zone before he bagged the winner.
He added: "A player of that calibre you can't let him have too much room in the box and he got a little bit too much room and finished it well, but we're massively disappointed and we want to go again."
Central defender Richard Keogh came close nine minutes from time when he got his head to Aiden McGeady's cross, but Poland goalkeeper Lukasz Fabianski claimed the ball at the second attempt.
Republic boss Martin O'Neill said of the chance: "I've seen it back and I'm naturally disappointed because I thought Richard probably would have scored and it is disappointing. We knew that at some stage or another, particularly in the last 15 minutes, that we would get an opportunity to score a goal.
"That was it. We didn't take it. It's gone but we live to fight another day."
With the defeat and a look towards the play-offs, O'Neill added: "It was always going to be a difficult game for us and here we maybe didn't have the same energy as we did against Germany and, with the short turnaround away from home, against Poland it was going to be difficult.
"Having said that we probably made life difficult for ourselves at times.
"I'm saying all of this, but we're still in with a chance. We've got two games coming up and we can still make it. We're just disappointed because the win against Germany gave us a run at it this evening and we weren't quite able to do it despite putting an awful lot of pressure on Poland."