Manning explained during an appearance on The Rich Eisen Show losing games started to take a greater toll during the latter stages of his 16-year career:
"On Monday morning, physically I feel a lot better and mentally it's not as draining. I'm not dreading the week. I'm not dreading going into a meeting and thinking about this terrible throw I made, and not having to deal with the losses. The losses got tougher and tougher to deal with and to overcome and so I just got tired of it.
"I was ready to be done playing in February when I retired and I knew I was done playing football. I still have those same feelings. I'm happy where I am, sitting on the couch and watching these games on Sunday."
The two-time Super Bowl champion also confirmed there were no thoughts of a comeback, saying he didn't continue training in the offseason with hope a call would arrive:
"No, I think I was done. I had my run, I had my time. I enjoyed it. I have such great memories. ...
"I'm good where I am. I made that decision in February. I'm not gonna look back. I'm not gonna second-guess. I wasn't working out for football and thinking there might be a comeback if someone called. I'd had enough and grateful for my time, but looking forward to this new way of life."
The four-time Pro Bowl selection told Eisen the fact he would have been forced to change teams at such a late point in his career was also a factor in his decision to step away.
Manning's performance dropped off across four appearances last season as the Giants shifted to rookie Daniel Jones as their quarterback of the future. The Ole Miss product completed 61.9 percent of his throws for 1,042 yards with six touchdowns and five interceptions in his final season.
It's his play over the first 15 years, highlighted by the two championship triumphs over the New England Patriots dynasty, that should land him in the Pro Football Hall of Fame.