Turns out you've been filing your nails wrong this whole time. Use this intel from a professional manicurist to get stronger, healthier nails every time.

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On first dates, job interviews, board presentations, and anytime you post a photo to Instagram, all eyes will eventually wander to your hands. And more specifically, to your nails. That’s partly why it’s so important to maintain your nail health and make sure you don’t experience breaking or peeling. Not only does that make you look sloppy and unkempt, but nail breakage can also be quite painful and even invite infection if nails break too low.

To keep nail breakage at bay, it turns out nail filing is part of the problem and the solution.

Filing can introduce problems if you don’t trim your nails first, according to Erica Marton, celebrity manicurist in Miami and New York City. “Taking down the length with a file can cause too much stress on the nail, which encourages breakage or splitting, especially if you have longer nails,” she says. Marton suggests trimming nails to the desired length and then filing them into proper shape. Filing can also weaken nails if you use a back-and-forth sawing motion. “Stick to one direction only in this three-step process: File side to center, where you go on the side of nail to the tip at a 45-degree angle, then the other side to the tip, and then finish at the top of the nail,” Marton explains. “But do not file too much of the sides, which could encourage tears,” she adds. “Use a light stroke and make sure you soften off the corners of nails.” And never file just after you’ve gotten out of a shower or bath. Wet nails break more easily.

Filing the right way will smooth the edge of finger nails, which are laminated layers of protein called keratin, according to Marton. These best practices can actually make nails healthier:

Use the right file. For natural nails, Marton says it’s best to use a higher grit number to prevent tearing. She usually opts for a 180 grit, but says if you’re new to filing, try a 240 grit. “I like Tweezerman Neon Spot FileMate, plus it comes with a nice carrying case,” Marton says. “For weaker nails I recommend Diamancel—it’s a great file for weak nails that won’t cause breakage and is not too harsh. Plus it’s durable and washable,” she notes. If your sister, roommate, or pal asks to borrow yours for a hangnail? Try your best to politely decline, since it’s not sanitary, Marton adds. (If you have a hangnail, here’s why you should never pick it.)

Stick to short. Though long talons are good for back scratching, tapping your nails impatiently in a meeting, and sporting super-fun designs, they aren’t the strongest. As Marton says, “any length past your fingertip can add too much stress to the nail bed, which leads to breaking.” As for the shape, Marton suggests keeping them square or round.

Whatever you do, always keep your nails clean and dry to prevent bacteria from growing under your nail bed. And try to avoid nibbling your nails—here’s why biting your nails is so bad! Use these other pro tips to grow your shiniest, healthiest nails ever.