For NFL players, the game of football is near impossible to leave behind. But there comes a point in every man's career where he has to walk away from the game that raised him.
Unfortunately, some NFL greats will be forced to take the plunge after the 2012 season.
Here are three players likely to retire after this year.
Detroit Lions' kicker Jason Hanson took the field as an NFL starter in September of 1992—before Bill Clinton had even been elected president—and his 20-year career, spanning three decades, will likely come to a close following the 2012 season.
The tenacious Hanson, who has missed just nine games since his professional debut, will push his physical limits to add a 21st season to his résumé.
Hanson suffered a knee injury in 2010 which caused him to sit out half the year. Last season, he almost missed a game after dinging his knee again, allegedly in an ATV accident.
But the biggest physical challenge Hanson will face is his age. Last month, he rang in his 42nd birthday, making him one of the oldest players in the NFL.
The kicker knows he'll face a tough season, but despite the challenge, he's not ready to walk away from football yet.
Hanson is determined to give it one more go, and it's hard to blame him.
Whatever ailments the 42-year-old NFL player might endure will be nothing compared to the 13 losing seasons (which include a brutal and much-mocked 0-16 record) he's had to face.
Hanson has another chance to be a supporting cast member of the Detroit Lions' show—starring Matthew Stafford, Ndamukong Suh and Calvin Johnson.
With the 2012 Lions looking like Super Bowl contenders, Hanson will stick around for one more season before hanging up his cleats.
While Baltimore Ravens' linebacker Ray Lewis has a way with words, it's hard to believe that "quit" is in his vocabulary.
Number 52 wasted no time quashing retirement rumors last season, announcing that he would remain a Raven through 2012 just moments after the Ravens lost in the AFC Championship game.
But physical ailments and extracurricular concerns could cause this season to be the legendary linebacker's last.
The 13-time Pro Bowler's body has begun to break down. After sitting four games due to a toe injury last season, he looked worn out upon his return to the field.
Ray Lewis is undoubtedly the most physically tough and constantly motivated player in the NFL, but there's only so long a decrepit athlete can perform on will alone.
Lewis will fight for his starting role in 2012, but even if he succeeds, his body may not let him play it for much longer.
But it isn't just Lewis' aging body that could extinguish his NFL career—personal reasons might motivate the future Hall of Famer to leave after this season as well.
Retirement would allow Lewis to spend ample time with his family, which he has admitted is an enticing prospect.
Lewis has also said that he can't see himself playing football past age 37, and a comment like that is usually not something said on a whim—it is often thought out and mulled over.
Lewis turned 37 in May of this year, meaning that, if he's true to his word, this year will be his last. An 18th NFL season would mean playing past 37.
And finally, Lewis has admitted that he only remains in the NFL for the prospect of a second Super Bowl victory.
"I only play this game for another ring," Lewis told CBS Sports before last season.
For a champion who has already established enormous shoes and an unfaltering legacy, the prospect of a second Super Bowl ring might be easy to walk away from next year in the face of physical deficiencies and familial need.
San Francisco 49ers' wideout Randy Moss has achieved virtually everything that NFL receivers dream of on draft day—except a coveted Super Bowl ring—so it's not much of a stretch to think that Moss' return to the NFL is the result of a one-track mind.
There is no way Moss would have joined the Niners if they were not Super Bowl contenders or if he did not have the potential to be their No. 1 receiver.
And that's a fair standard for a retired 35-year-old who's already hoisted his career to the top of the record books.
The 2012 season is Moss' last-ditch effort to nab some bling, and he has every right to compete for that.
But it seems pretty obvious that if the 49ers win the Super Bowl, Moss will walk away from the NFL, finally vindicated after a 14-year career.
And if the Niners don't take home the ultimate prize and Moss struggles, he is likely to unleash his prima-donna tendencies, extinguishing all hope of another free-agent signing in 2013.