While the two-time Super Bowl MVP quarterback has felt it before, this time it has been a little more intense because Manning told a running back not to score late in the contest.
It certainly was not the start the Giants needed after missing the playoffs the last three seasons.
It's no wonder that Manning was grilled Wednesday about overcoming such a tough loss. He was asked if he talked to his brother, Peyton, for advice. Had he communicated with dad, Archie? How did he feel? What were his emotions?
He answered every question. He even smiled a bit when asked if anyone had disowned him.
''I'm over it,'' Manning said. ''We've moved on. As soon as you start game planning for the next team and starting to take your notes, and get ideas, and see how you're going to move the ball, make plays, buy completions, your mind gets on the next week and doing what you've got to do.''
The Giants' focus this week needs to be on Atlanta, which stunned Philadelphia in giving new coach Dan Quinn a win in his first game as a head coach.
The Giants can't afford another loss.
''Anytime you lose a game, it's tough,'' Manning said. ''You can lose for different reasons or plays you want to take back. But yeah, you're disappointed about it or you feel like you let down your team. But you bounce back, you get over it, and you go to the next game.''
That thought was a major part of coach Tom Coughlin's address to the team this week. It's a time to move on.
Guard Justin Pugh said the players have talked about what happened at the end of the Dallas game. It's hard not to discuss it.
''But it's something where you realize that there's a lot of different things that go into it,'' he said. ''And if we would have put seven points on the board at different points in the game, we wouldn't have been in that situation. Everyone wants to put it on one guy, and that's just totally unfair. We're a team in here, all 11 of us could have done things differently during the game. That's just the way it is.''
The one person who was not around to discuss the situation Wednesday was halfback Rashad Jennings. He was the one who told the media that Manning told him not to score with New York ahead 23-20 with less than two minutes to play. Manning felt it would milk the clock, believing Dallas had only one time out. It had two and a third-down incompletion gave Dallas a chance to steal the game.
In 20-20 hindsight, Jennings probably should have kept quiet. He has since apologized.
''Rashad didn't do anything wrong and we chatted and talked,'' Manning said. ''We're great, we've moved on from it, and now we're going to play football.''
To win, the Giants need more out of their offense, and the defense can't fold late. It gave up touchdowns on Dallas' final two possessions.
''You know it's just unfortunate the way the game ended, but it is what it is,'' receiver Odell Beckham Jr. said. ''There's nothing we can do to change it now.''
NOTES: Receiver Victor Cruz (calf), linebacker Jon Beason (knee), defensive tackle Markus Kuhn (knee), defensive end Owa Odighizuwa (foot) and tight end Daniel Fells (foot) did not practice. Offensive tackle Ereck Flowers (ankle) and linebacker Uani Unga (knee) were limited. Flowers said he expects to be ready for the Falcons.