Ask Brianna: Do I Really Need a Budget in My 20s?

With a budget, you won't spend your whole paycheck — after you've paid rent and bills — on dinners out and Amazon impulse buys.

"When thinking about budgets, people usually default to thinking about how to cut their everyday consumption," says Hui-chin Chen, a financial planner and co-owner of Pavlov Financial Planning in Arlington, Virginia.

Living in an apartment, driving a car or making a student loan payment you can't afford is more problematic.

Federal student loans come with income-driven repayment plans that will let you pay a certain percentage of your income each month to keep your bill affordable.

Stick with roommates, and hold off on moving into a luxury apartment building if that would increase your housing costs to 30 percent or more of your income.

Another way to make sure you don't overspend is to come up with a savings goal first, then back your way into a budget that allows you to hit that goal, Crary says.

Some of your savings should go to an emergency fund until you've got at least $500 put away for unexpected expenses, such as medical costs or car repairs.

The rest can go to a savings account that you'll use to hit other goals like travel or a down payment on a house.

The amount you have left over is often called "disposable income," or what you can spend on nonessential expenses, like shopping and entertainment.