Senior man looking sad © George Doyle, Stockbyte, Getty Images

Tomorrow, like every day, about 10,000 Americans will retire. And many of them will mess it up.

Financial advisers cite a long list of the big mistakes new retirees make as soon as they hang up their tools or turn in their BlackBerrys.

Most are avoidable, often quite simply.

1. Mishandling Social Security

Many people rush to collect benefits as soon as they are eligible, at age 62. But there's a cost. By taking it early they will collect less each month -- a lot less. Those who delay until age 70 can boost their checks by as much as 70%.

Those who take Social Security early usually make a simplistic calculation: "I may collect less each month, but I will collect it for longer, so it sort of works out over the long haul," they reason.

But it's flawed thinking. Robert Gerstemeier, a financial adviser in Chicago, notes that those who delay will collect more provided they live beyond about age 80 to 82. Among today's new retirees, many will.

Furthermore, those who take Social Security early are giving up something very valuable -- longevity insurance.

Many people today risk living into their 90s or even later. The real financial-danger years for those who do will be the later ones, when a lot of the savings may have been used up and medical costs are skyrocketing.

A larger Social Security check could be a real help if you live well beyond your life expectancy.

Taking payments too early is the most common Social Security error, but it isn't the only one, say advisers. Sometimes married couples can obtain higher benefits by structuring when and how each spouse claims, they say. Those planning to take Social Security need to investigate their options before they file.

2. Splurging on big-ticket items

New retirees suddenly find they have time for all those projects they didn't get around to when they were working, notes Bryan Wisda, an adviser in Carefree, Ariz. And this, he adds, can be a real problem.

He sees people suddenly blowing $50,000 on remodeling or other projects. The problem: The retirement portfolio may need to last for decades. The first dollars you take out are the most expensive, because you forgo all the future returns on those dollars.

The same argument goes for those who suddenly splurge on a boat, a new car or a bigger home they've always wanted. Marc Roland, a financial planner in San Diego, observes a trend among new retirees to trade up to a "dream home" when they retire.

Often they can't afford it, he says. They "are putting way too much into an asset that doesn't help pay for retirement."

John Sestina, a financial adviser in Columbus, Ohio, advises clients to make bigger-ticket purchases, such as replacing their cars, when they are still working and may be better positioned to handle the extra cost.

3. Not making a budget

It isn't just the big-ticket items that will burn you. Michele Clark, a financial planner in Chesterfield, Mo., says that some of her new clients are recent retirees "who called me and said, 'Help, we're bleeding money.' "

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They thought they could afford to retire, she says, but "they are stunned by how fast they are seeing their checking-account balance go down."

They no longer have a steady paycheck -- and now they have a lot of free time on their hands, during which they can spend money.

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