Manning also sounds rejuvenated by the process of learning a new offense under new coordinator Ben McAdoo.
"It is tough, it's not easy, but it has definitely re-energized me and brought an urgency to this time of year," Manning said Tuesday, on SiriusXM NFL Radio.
The two-time Super Bowl MVP is coming off arguably the poorest season of his career, if you toss out the nine games he played in his rookie season. Manning threw for just 18 touchdowns, with a league-high 27 interceptions, and a quarterback rating of just 69.4 in 2013.
His work ethic has never been questioned, but it sounds like Manning's working even harder than usual.
"It's definitely challenging. Each night, I'm staying up and preparing, and I feel like I'm in season right now with the amount of preparation I'm trying to put in to get ready for each practice," Manning said.
"Each practice is draining on you mentally, you're thinking so much about everything that has to go on and the different calls," the quarterback continued. "But it is also exciting. As a football player, as a competitor, you like to be challenged."
The Giants have two more organized team activities, on Thursday and Friday, followed by a mandatory three-day minicamp next week. Manning has been able to participate fully in the team's first eight OTAs, despite undergoing ankle surgery in April.
That should pay dividends, as the 33-year-old prepares to play under a new offensive coordinator for the first time in his career.
"This has been huge, just getting in the offense," Manning said. "It's one thing to listen to a play being called or watch plays being run -- you may think you have a good grasp of it, until you're out there and you gotta pull the trigger, you gotta make a call, you gotta change a play and you’re doing it live, and with the defense, and make all those little decisions. It was huge."