When you're in your 20s--especially your early 20s--you feel invincible. You can eat what you want, live on tequila and go without sleep for days at a time and you'll still look fresh-faced. Well, in the short term, at least. The long term is a different story. As far as your health and looks go, what you do at any age in your life will affect you later in life.

Take sun tanning, for instance. It will age your skin, fast, because tanning equals wrinkles. No two ways about it. Wearing heavy earrings? How does lobe surgery sound? Wearing high heels too often can irreversibly damage the tendons in your legs, and toting a heavy purse around on one shoulder can lead to shoulder damage that may force you to carry around a backpack. Sexy, huh?

What you do in your 20s matters. Read this article for more proof.