Owning a home
Even though real estate values range widely, being the master or mistress of your own castle is definitely a middle-class thing.
With the cost of medicine skyrocketing, it's imperative to have insurance and the middle class does.
Owning a car
Middle-class folks don't rely on public transportation unless they happen to be ecologically conscious and use mass transit to save the environment.
Not everyone can afford a two week family holiday every year. Feel fortunate if you can, even if it means having to deal with the airlines.
Sending kids to college
You don't have to be a Rockefeller to pay for college, but it sure helps these days. Still, middle-class kids continue their education after high school.
Middle-class people don't work until they drop. They're able to retire and even move to warmer places, like Florida and Arizona.