
Sun Damage
The most immediate indication of skin damage is a sunburn. Not only are they painful (and sometimes embarrassing), they are really bad for your skin. If you looked at sunburnt cells, you'd see the significant damage. Over the years, your skin will turn old, dry, and leathery. And although it looks "tougher," it's actually more fragile.
Finally, over time, you could easily get skin cancer if you spend time in the sun without protection. Although largely treatable, skin cancer is something you don't want to deal with.
Sun Benefits
It is true that exposure to the sun will help you obtain vitamin D; however, these days, vitamin D is included in many common foods – so you shouldn't use that as an excuse to go out without protection.
Protection
Even on cool and cloudy days, the UV rays from the sun will still make its way through and attack your skin. When outdoors, either wear sunscreen (with at least SPF 15) or cover up with clothing. Long sleeves, hats, shades, and sunscreen will protect your skin from damaging rays and keep your skin healthy and younger-looking on a long-term scale.
Protect that beautiful body of yours and stun your classmates with your gorgeous skin down the road. Make it look like you showed up to the wrong class reunion!
Photo credit: http://ladyartlooks.com/