This week The Motley Fool ran a piece about a problem no retirement calculator will show you: the fear of running out of money, and what happens when that fear stops being a useful instinct and turns into a permanent condition. You can read it here, and I'd suggest you do, because it names something I've watched in friends and readers for years.

The article calls it hypervigilance. Checking balances daily. Running the numbers every weekend. Feeling a pang of guilt over a dinner out. Retirement was supposed to be the reward. Instead some people spend it doing the same anxious arithmetic they did at forty, except now there's no paycheck coming to settle the argument.

I understand the fear. It's rational to a point. Most of us spent thirty or forty years saving, and the muscle we built, spend less than you earn, stay the course, doesn't come with an off switch. When the paychecks stop, the muscle flexes harder.

Now the math that usually calms people down. Withdraw 4 percent of a diversified portfolio in year one, adjust that dollar amount for inflation afterward, and history says the money has lasted thirty years in the overwhelming majority of periods, including ones that started right before awful crashes. Not every period. Most of them. And if the market drops 20 percent in your third year and you keep withdrawing the same inflation-adjusted amount, you're selling shares at lower prices, which hurts, but the historical record says the portfolio generally recovered before the damage became permanent.

The people who get hurt are usually the ones who panic at exactly the wrong moment, or the ones who never saved enough in the first place and are trying to budget their way out of a math problem. Two different problems. Fear blurs them together.

The practical fix is boring. Pick a withdrawal rate with a margin of safety, maybe 3.5 percent if you want extra cushion. Rebalance once or twice a year. Check your accounts on a schedule, monthly at most, and then live your life. I knew a man who checked his portfolio every single morning with his coffee. Died with plenty of money and a decade of mornings he spent worrying instead of fishing. Nobody warns you about that trade.

My own plan is simple. The bills come from dividend and interest income and modest withdrawals, the portfolio gets rebalanced on my birthday and in the spring, and I gave my wife explicit permission to tell me when I'm being ridiculous about a purchase. She's cheaper than I am, so the system has a natural brake.

If the fear is persistent enough that you can't enjoy money you plainly have, that's worth talking to a professional about, and I mean a fee-only planner or a counselor, not somebody selling annuities at a free steak dinner.

You saved for decades so you could stop worrying about money. Don't let the worrying follow you into the part you paid for. As always, this is my perspective, not professional financial advice.