When I first started working at 16, I saved up what little money I made. When I turned 18, I started working even more to pay off some of my tuition and make a car payment. I remember telling an older coworker that every 6 weeks or so, I splurged and bought $100 worth of CDs online. He laughed and told me that he used to be able to do that, before he had to worry about rent, student loan payments, yadda yadda. And years later, I make far more than I did at 16 or 18, but have actual bills to pay.
Also, when I bought an iBook 4 years ago, it was a greater accomplishment than buying my recent MBP...if only because I made far less money and I had to scrimp and save for that. Nowadays, I just had to save for a few weeks.
So if you make a few crazy purchases in your teen years, don't worry about it, as long as you have the money to pay for it. You'll make a lot more money some day...but you'll also have a lot more obligations. Might as well enjoy your money when you're young.
And just borrow the $25!