Getting your nails done, a new outfit, a night out, dinner, these are all ways to treat yourself. Treating yourself is a must when you have a job. It's a way to reward yourself for your hard work as well as show yourself that all the money you're making isn't just for bills and your college tuition.
Even if you get something small, treating yourself should be a necessity. It always makes me feel happier when I treat myself to something after I get paid. Now maybe I treat myself too much sometimes, but it really boosts my happiness. Whenever I go out and buy myself something, I instantly feel 10 times better. I know I'm not the only one, either. Ever heard of retail therapy?
Another reason you should treat yourself is because it shows you how hard you worked. It's like a blue ribbon. Go ahead, splurge on those sunglasses. Show yourself, and others, how hard you worked. It will motivate you more to work harder next time around. Maybe you'll pick up some extra hours or ask for that raise.
In the end, treating yourself should make you feel GOOD, not guilty. So go ahead and buy it. Just make sure you pay your bills as well. Treating yourself is fun!