Idiom: to live within one's means (used as a verb)
Angela is in debt. She hasn't been living within her means this past year, using credit cards to pay for everything. Now she has to move back into her parents' house so she can save money on rent and use it pay off her credit cards instead.
Meaning: The expression "to live within one's means" means to only spend the money you have. In the example above, Angela was not living within her means, so she built up excessive debt.
Tim: Hey, want to hang out tonight? I heard about this great new restaurant
Brad: No, I'm trying to save money, so I'm not going out to eat.
Tim: But you can go out occasionally.
Brad: I've been focusing on living within my means. I paid off all my credit cards, and I don't want any more debt.
Tim: That's responsible of you.
Brad: But if you want, we can still hang out. We can make dinner at my place.
Tim: That sounds cool. What time should I come by?
Meaning: In the second example, Brad says that he is trying to live within his means. He has paid off his debts and is trying to avoid any more. This means that he will only spend what he has.