8 Big beauty sins

Rehab: Keep the skin around your nails moisturized, says Vartoughian. "If it's hydrated, you'll have fewer snags and be less tempted to pick at it." Rub a thick cream or oil into your cuticles daily and massage them with an exfoliator every few days. Also, push overgrown skin back with a cuticle stone after showering, when they're soft. You can also try a bitter-tasting nail polish designed to keep you from putting your fingers in your mouth.

2. Swapping Your Strand Shade Frequently

Why it's a no-no: Trading your tress tint occasionally is okay, but dyeing your hair too often can make it weak and lead to an identity crisis. Sure, celebs like Rachel McAdams and Ashlee Simpson constantly switch up their hair hue, but they do it for a movie or to capture attention on the red carpet. And they put in major moolah and extra TLC to undo or hide the damage.

Rehab: First, try diverting your desire for novelty from hair color to makeup, since it's easier to experiment with lipstick and shadow on a weekly basis. And when you get to the point that you just have to color your coif, take this advice from Pantene celebrity colorist Rita Hazan:

• Be a smart blond. Bleach is the most damaging and drying ingredient. It's okay to hit the bottle once every six weeks if you're only brightening up a shade or two. If you want to be lighter than that, use a bleaching kit once a month, going one level blonder each time until you reach your desired hue.
• Going darker is less damaging. Adding color to your hair isn't as stressful to your strands since you aren't stripping away any natural pigment. You can use a permanent dye every four weeks and an ammonia-free semipermanent formula every three weeks.
• Crib a conditioning regimen. Postcolor, apply the kit's deep conditioner. Also, use a hair mask once a week.