Almost exactly 50 years ago this week, I got the first big shock of my more-or-less adult life. I was handed my very first paycheck … and it wasn’t all there.

I’ll bet you remember that moment, too. You’d put in your time for some agreed-upon sum — for me, a buck-something an hour — and multiplied your reward out in your head, planning exactly how many record albums, gallons of gas and boring necessities you’d spend it on.

But rather than the expected amount in the high double digits, the prize finally in your hands fell considerably short of what you’d expected.

Welcome to the world of payroll deductions. Back then, Old Age, Survivors and Disability Insurance — Social Security — was the furthest thing from my mind. I was more interested in acquiring “Sergeant Pepper’s Lonely Hearts Club Band” than squirreling away one single penny for some theoretical “golden years.”

The missing money didn’t really amount to much, looking back — 3.9 percent for OASDI and 0.5 percent for Medicare (introduced just the year before) — but still, it stung. I mourned my missing $3.20, just a quarter shy of covering the vinyl LP I so coveted.

Now, at last, the circle has closed. A few days ago, I found myself in the windowless, rather grim Social Security office on the third floor of the Federal Building in downtown Fargo, signing up to start the flow of the benefits I’d once pigeonholed to think about in the unimaginably distant future.

Until last week, Congress’s perennial bitter debates over benefits seemed pretty abstract. Of course, I did have an opinion (as I do about most everything): All those long-laboring, exhausted old folks had earned their monthly pittance with a lifetime of labor, plus a lifetime of taxes to pay for it. Social Security certainly sounded like a good thing … for someone else in that crowd of old folks I vaguely knew must be out there somewhere.

But now that I’m a new recruit myself in that elder army, I see the proposition far more plainly. It’s my money. Give it back.

I’m still pretty new at this “old” stuff. Enter AARP, the fearsome force that’s been tracking me for years and years, ever since my far more senior husband (by 26 months) turned 50. When I showed up for its pleasant May workshop in Fargo, I was amazed: first, at how simple they made the big step sound, and second, how my hundreds of peers who filled the room could all look so much older than me.

Fantasy aside, I gleaned insight into the crucial next step: Enroll online at mysocialsecurity.gov.

Easy enough — until I realized how much more the government knows about me than I do myself. Registration required proving who I was by answering several deceptively simple questions. Could I pick out the lender for whom I co-signed my daughter’s college loan in 2003? Nope. The issuer of our mortgage, which had bounced like a ping pong ball between corporate mergers until we paid it off nine years? Huh uh. The blighted address where I’d lived on for two months as a college sophomore? Are you kidding?

I flunked a quiz on my own life. That barred me from moving on to the next step. I needed to consult someone who knew more about me than I did. And where might I find such an all-knowing, all-seeing guru? Big Brother!

Which is how I found myself tapping a touchscreen kiosk in the Social Security suite and taking a number. Eventually I stood in front of a patient, helpful young woman as I explained my dilemma, which sounded suspicious even to me. She spoke very slowly to make sure Grandma understood, reviewing my IDs and ultimately concluding that I was indeed the ancient human whose name they bore. She gave me a printed code to bypass the online test that had proven too tough for me — then shooed me home to my computer to finish.

But that wasn’t all. Just to make sure I’d been listening, I received no fewer than five letters from Washington, D.C., over the course of the next seven days — each addressing one, and only one, point. One confirmed I’d visited the office. Another instructed me, as she had, to go online to wrap up my registration. A third — same date, a few minutes later — confirmed that I’d done exactly that. But the most interesting of the five was the one I opened last, a dire announcement that I’d been ruled ineligible for one particular type of payment to low-income people who’ve never worked. The reason, listed two lines farther down: “You told us you do not want to file a claim for SSI.” Yes, that would do it.

Now, duly enrolled as an official old person, I could examine the meticulous records the feds have kept on every penny I’ve earned through the past half-century. I could also see, with blinding clarity, the payroll taxes squirreled away for this day when I’d finally be deemed — um — mature. Humbling … all those years of getting up early and working late, reduced to a pretty short list of brazen figures! I could also see, bite by bite, the six-figure sum Social Security and Medicare have chomped out of my earnings. (Since I’m mostly self-employed, I’ve had the honor of paying twice as much as you wage slaves, thanks to rendering both the personal and employer’s shares of what’s due unto Caesar.)

Yes, I may have griped about those deductions — oh, a gazillion times or so since the first time in June 1967. But suddenly — now that I’ve achieved that perfect degree of personal ripeness — it doesn’t seem so bad. For many of those years while I was younger, haler and heartier, my dollars were not only funding benefits for the good retired folk in line ahead of me … but piling up the nice surplus my generation helped amass.

Mingled deep in the national budget, my paltry contribution was being used, as intended, to maintain generations of grandmas and grandpas before me. That its excess was also squandered on pointless wars and other national schemes along the way does nothing to negate the promise that’s undergirded our expectations for our future.

Now, when Congress is panting for budget cuts, the “old age, survivors and disability insurance” in which we’ve invested has mysteriously morphed into someone’s idea of a government handout. Entitlements? I beg your pardon. Those benefits are mine, and yours as well — regardless of whether lax caretakers have frittered away the principal!

Now that I’m officially inducted into America’s elder army, watch out. Thanks to the feds, I’ve reconnected with every Hanson dollar piled up along the journey from my first paycheck to demi-retirement, and I’ll be happy to take on anyone who dares consider my imminent checks — and yours — a “handout.”

When the fearsome AARP army marches on Washington to take on our sleazy foes, look for me in the first battalion. Keep your grubby budget-slashing fingers off of my Social Security, you sniveling hounds! Now it’s personal.