As Tay, El, and Kevin have already pointed out: it is all about budgeting. You really have to learn how to plan. Do I want to spend $30 and go to the carnival today, or spend $30 and go hang out with friends? This is especially important once you hit college and your parents can't exactly say "no" as easily as they could before.
I mean yeah, it might seem a bit rough, but once you're more independent and actually realizes how far you may have to stretch your money, you'll realize the importance of budgeting.