The idea of anything creeping in unnoticed is enough to unnerve the bravest among us.

In the world of personal finance, it's the subtle, sneaking changes in spending habits that may be most chilling. The phenomenon is known as lifestyle creep, and it's one of the biggest — and most overlooked — barriers to building long-term wealth.

However, once you know what to look for, there are strategies for keeping lifestyle creep far, far away.

"Folks agonize over negotiating pay or maximizing their returns by just a couple percentage points, but it's lifestyle creep that kills a lot of folks," says Ami Shah, a certified financial planner in Washington, D.C., and CEO of Steward, a financial planning software tool.

As income rises throughout your career, often expenses will, too. More disposable income might mean signing up for another streaming service or eating out more frequently. Or it could mean buying a second home or a new car.

And it's here, "when your expenses continuously increase in lockstep with your income," that lifestyle creep can set in, Nilay Gandhi, a CFP and senior wealth adviser with Vanguard.

There are several ways to keep lifestyle creep at bay. The best place to start is to create a financial plan and a budget, and stick with both.

For Shah, the first line of defense is to not overspend on housing, often someone's largest expense. Generally, she suggests that clients keep housing costs below 25% of their net income. And if the amount they're saving falls below 20% of their net income, that could be lifestyle creep crawling in.

Earning a raise is a great opportunity to ward off lifestyle creep, Gandhi said.

He advised putting a certain percentage of the raise — 75% is a good rule of thumb, he said — into a pot that will help you meet your financial goals, whether that's retirement, stock investing, saving for a down payment or paying off debt. Then, whatever's left is yours to use however you want.

"This approach still allows you to reap instant gratification from every raise," he said. "You have 25% to allocate to your budget as you see fit while ensuring 75% is put towards your goals."

This, he said, is one of the best ways for anyone to set themselves up for financial success while evading the subtle-yet-destructive march of lifestyle creep.

Chris Davis writes for NerdWallet.