The couple is no longer able to cover all of their monthly expenses -- including the mortgage, car loans, home repair loans and student debt -- with their paychecks alone.
"I watch every month our savings deplete," said Karhinen, who lives in Queensbury, N.Y. "I'm realizing we're not young enough to save a lot."
The downturn in the housing market also hurts. The couple bought their house in 2006, hoping it would serve as an investment and help support their retirement. But now, they would only break even if they sold it, she says -- if they were lucky.
The mortgage crisis "hollowed out" the middle class, said Tamara Draut, vice president of policy and research at Demos, a public policy research organization. Much of their wealth is tied into home values, but national home prices are still 29 percent below their mid-2006 high, according to S&P Case-Shiller.
That means some folks have lost all their home equity and may never get it back. Others can't take out loans to finance repairs, college for the kids and other expenses.
There's one more big squeeze hitting households: health care. Since 2002, insurance premiums have increased 97 percent, rising three times as fast as wages, according to Kaiser Family Foundation/Health Research & Educational Trust.
In Mississippi, Bruister now has an $1,800 deductible, compared to $500 a few years ago. When she goes to the doctor, the bill typically tops $100 -- so she tries to avoid going.
"Health care for me has turned into more of a luxury item," said Bruister, 52. "I go every year for the checkups my insurance pays, but after that you just tough out the other illnesses."
Economists say they don't expect much improvement for the middle class any time soon. The recession is officially over, but the recovery is fragile, and its gains aren't evenly spread. Between 1993 and 2011, the top 1 percent of America's earners saw their income soar by 58 percent, while everyone else only got a 6 percent bump.
That's making it even harder for most households to get ahead.
"The middle class was always synonymous with economic security and stability," Draut said. "Now it's synonymous with economic anxiety."