You've heard it before: Pay off your credit card debt as soon as you can, so that you don't needlessly hand over fistfuls of your hard-earned money in interest to the card-issuers. I understood that advice, but I didn't fully appreciate it until I read a startling post from Fool Community member ClimbingOut on our Credit Cards and Consumer Debt discussion board.

Like many people, ClimbingOut was delighted to enter the world of credit card ownership. He enjoyed charging whatever he wanted, with little regard for whether he could afford it. His debts piled up. He had trouble paying the rent. He took out payday loans. The amounts he owed to credit cards and American Express (NYSE:AXP) increased. He went to school and took out student loans. He eventually moved into well-paying jobs, and worked on paying down his debt. He never ended up dealing with collection agencies, and didn't hang on to debts longer than five years. In short, it seemed like he was managing his debt rather well.

But some reflection changed his mind: "I turned 35 last year and took a good hard look at my life. 401(k) balance: minimal, no other retirement. Manageable debt that left me with a little extra spending cash each month. Basically spinning my wheels. Why? How could this happen? I made good money, I should be in a better position than this! Look at my finances! One slightly major problem and I'm wiped out!"

Here's what blew him away, though -- he recently calculated how much he'd paid in interest over 20 years: $193,345.59. "And that first purchase? An awesome stereo system. Not a rack type of system, but one of those all in ones. A glorified boom box that I just had to have. Lasted one year. And the damned thing ate my favorite tape."

Fools respond
So there you have it -- evidence of just how much damage irresponsible borrowing can do. ClimbingOut has received a lot of support on our discussion board, though, as he continues to turn his life around.

TMFJeanie wished his post "could be reprinted and included in the orientation package of every incoming student in the U.S." She also pointed out a sad reality: "[J]ust imagine if the $50 here and $80 there in monthly interest payments to credit cards had instead been contributed to an IRA account. Invested in even the most conservative of funds over 20 years, you'd now be a 35-year-old with a huge head start on early retirement."

OtherVoices offered an interesting way to look at it: "I think seeing that figure is an amazing kick in the teeth. Can you imagine 20 years ago saying to yourself, 'I'm going to spend $193,345.59 extra on everything I buy'?"

Those are indeed great points. Imagine, for example, that he'd invested just $3,000 in stocks 20 years ago. In Boeing (NYSE:BA), it would have grown to more than $32,000. In Procter & Gamble (NYSE:PG), it would have become more than $55,000. And given his interest in computers, if he'd parked that $3,000 in Intel (NASDAQ:INTC), it would have grown to more than $85,000. In Microsoft (NASDAQ:MSFT)? More than $375,000. See how credit card debt is like investing -- in reverse?

Get your act together
Think about your own situation now. Are you saddled with high-interest-rate debt? If so, are you managing it well -- and paying it off soon? It's not uncommon these days for credit-card companies to be charging rates of 25% or more per year. At that rate, if you owe $40,000, you'll be paying $10,000 just in interest each year.

You can learn much more about the surprisingly interesting credit card industry in our Credit Center, which also features tips on getting out of debt, along with guidance on how to manage your credit effectively. Really. I mean it. There's some great stuff in our Credit Center, and it's all free reading.

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Longtime Fool contributor Selena Maranjian owns shares of Microsoft. Intel and Microsoft are Motley Fool Inside Value picks. The Fool has a disclosure policy.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.