Popsugar Living Advice People Share the Things They Wish They'd Known at 21 People Share What They Wish They'd Known When They Were 21, and It's Such Good Advice January 23, 2020 by Erin Cullum View On One Page Photo 12 of 21 ADVERTISEMENT () Start Slideshow Share This Link Copy ← Use Arrow Keys → 12 Wear Your Retainer Just do it. It's way better than getting Invisalign or braces down the road. Previous Next Start Slideshow AdviceCollegeWellnessSelf Improvement