We all do it, if we're being honest.
With the passage of each decade, each time our ages have a zero on the end -- or even begin to creep closer to it -- we take stock.
Where are we? What have we done? Where are we going? Are we where we want to be?
Often, it's a simultaneously rewarding and harrowing exercise. Even in the celebration of accomplishment, there's recognition that the climb is never complete. The mountain continues to rise, and rise, in front of us.
With that in mind, the magic number for the upcoming College Football Playoff is 39.
That's the age of four of the coordinators coaching in the semifinals: Alabama's Lane Kiffin and Kirby Smart, Oregon's Scott Frost and Ohio State's Tom Herman.
Kiffin, Smart, Frost and Herman will turn the Big 4-0 in 2015, and each man finds himself in a different phase of the wild, weird coaching life.
Their varied career stages illustrate hiring trends and the fact that most coordinators, including these four, have thought often of becoming a head coach.
One has already experienced it. And failed.
Clearly, Kiffin has a different perspective than the others, already having been a head coach in the NFL, the SEC and at his "dream job" -- USC.
Prior to 2014, the "stock" taken was that Kiffin won 40 and lost 36 games in those three jobs. He left Tennessee after one season, chapping fans in the process. He was fired in the middle of his second season with the Oakland Raiders and the middle of his fourth season at USC.
Even at four games over .500, arrogance and failure are words often used in coaching circles to describe those Kiffin tenures.
The silver lining: The guy knows offense. Nick Saban was aware of that, telling then-coordinator Doug Nussmeier to seek other employment so that he could open up a spot for Kiffin.
"No one questions the guy in terms of intelligence, what he knows [in terms of] X's and O's," another SEC coach said. "He has a mind for it."
Having Kiffin and Saban share a sideline created for some angsty, made-for-TV moments -- but the hire has been an undoubted success.
Alabama finished behind only Georgia in most SEC offensive efficiency metrics, including yards per play and scoring. And that was with an unproven senior quarterback, Blake Sims, figuring things out as he went.
Kiffin was a Broyles Award finalist, along with Frost and Herman. He didn't win, but he'd be a shoo-in for some sort of comeback of the year. Redemption is now part of his story.
Somewhere, someday, will Kiffin get another chance to lead a program?
"I'd think so," that SEC coach said. "He's still a young guy."
The question: What will he have learned, from his own failures and from Saban?
Frost is representative of the blossoming up-and-comer. There's nothing sexier right now to athletic directors than explosive offenses, and no program has been more consistently explosive the past few years than Oregon.
In Frost's two seasons as the Ducks' playcaller, they're averaging an FBS-best 7.45 yards per play. (Ohio State is second, at 7.10.) He replaced Chip Kelly in that role, by the way.
Quarterback Marcus Mariota, who just lapped the field to become the school's first Heisman winner, has been a big, big part of the continued success. But Frost has worked around a number of injuries, including one this season to top receiver Bralon Addison. Plus, the team's leading rusher was a freshman, Royce Freeman.
Frost got a look from Colorado State, Tulsa and others. He was considered a finalist at CSU.
Nebraska, Frost's alma mater, also needed a coach in this cycle. Some considered Frost a favorite, but Power 5 ADs are shying from coaches without head-coaching experience.
And following Bo Pelini, who won 71 percent of his games, would have been particularly tricky for a rookie head coach. Who's ready for that, really?
"The guy there before [Pelini] was winning, what, nine games a year?" a coach in the Big Ten said in early December. "How can you bring in [Frost] and expect him to do the same? That's completely unfair to him, if you ask me."
Frost didn't wind up being the guy there. AD Shawn Eichorst had Oregon State's Mike Riley in mind all along, evidently. But coaches have asked the same questions about Riley. Affable and likable as he is, Riley's teams have won nine games in a season just once since 2009. The Beavers were 5-7 in 2014.
So, if Frost feels he should have been considered more seriously, he could position himself for the next time that his alma mater is open. Even if things work well, Riley is 61 years old.
Herman is on fire right now. He's the "it" guy in coaching circles.
He was already on the verge, but then Cardale Jones, Ohio State's No. 3 quarterback in August, led the Buckeyes to a 59-0 rout of Wisconsin in the Big Ten title game. That's what elevated OSU to the No. 4 seed in the playoff. It lifted Herman, too.
Two days later, on Dec. 9, Herman won the Broyles Award for the country's top assistant.
Later that night, Herman interviewed with Houston athletic director Mack Rhoades, talking until 2 a.m. and convincing Rhoades that he was the man to bring back the UH offense to the levels it was operating at under Art Briles and Kevin Sumlin.
A week and a half later, on Dec. 19, a pep band played as Herman was introduced in front of donors and media at Houston. His wife and kids watching in the front row, Herman had reached a career pinnacle; he had his own program.
In a quieter moment later that day, Rhoades told Herman that he considered him for the UH head job three years earlier when Herman was Iowa State's offensive coordinator.
Timing is everything.
"You know what, you were right not to hire me," Herman said, responding to Rhoades. "I wasn't ready then. I'm ready now."
Herman said working with OSU coach Urban Meyer, seeing the ways that he ran his program, was vitally important for him.
"I wanted to be a head coach so badly," Herman said in his OSU office Dec. 1. "Had I gotten a job out of Iowa State, when I was there, I could have recruited and been the face of the program -- shaken hands with people and done all that -- I could have motivated a team, X's and O's we would have been fine.
"Where I would have failed miserably is the alignment and coaching of your staff. It has to be the same message being preached. It can't be different agendas. It can't be different languages.
"You can probably do it one way and win six, seven, eight [games a year], but to really get to the mountaintop ..."
Hey, remember him? Smart was a fixture in the past few coaching carousels -- a name that often surfaced for open jobs, big and small.
This time around, Alabama's defensive coordinator was largely a forgotten man, though sources say Colorado State and others were interested in him. He declined at least two overtures, they said.
Those who know Smart say he is still interested in being a head coach; he's just, go figure, content making more than $1 million a season and regularly competing for national titles while waiting for the right opportunity.
But there are forces working against him, and the coaching community acknowledges it.
"It's a world driven by offense," a Power 5 AD said a couple of weeks ago.
In a time when fan attendance is waning, ADs acknowledge that scoring points sure helps to put fans in the seats.
Coordinators are aware of the trends. One cited that Vanderbilt's Derek Mason was the only coordinator to get a Power 5 job in 2014. That hire isn't going well, which could further turn off ADs to coordinators, and DCs in particular.
The same goes for Will Muschamp's very visible failure at Florida.
"He had a great background at big-name programs like Texas," one AD said recently. "He's a good coach. ... But you can't learn on the job at Florida. You can start at an Autonomous 5 school, but probably not a top-10 job."
A middle ground can be found, with patience like Smart is showing.
Michigan State's Pat Narduzzi, a DC likewise overdue for a head job, is expected to be introduced Friday at Pitt.
Sources say Smart has asked around in recent years about South Carolina, when it opens. His alma mater, Georgia, will one day need another head coach as well.
Frost, Herman, Kiffin and Smart, at the same age but at different stages, each have so much promise. As the semifinals unfold next week, it's intriguing to project where each of the four coaches will be at age 49.
Who knows, perhaps they'll bring their own teams to the playoff.