You already know it’s a sin to go to bed without washing your face (right?!), but that’s just one of many common bad habits that can seriously screw with your skin.

To determine the most unforgivable beauty mistakes, we talked to board certified dermatologist Debra Luftman, M.D., co-author of The Beauty Prescription and dermatologist for Simple skincare. Brace yourself for some tough love—trust us, your skin will thank you later!

Mistake #1: You pile on the products We’ve all done it—you hear rave reviews about a new treatment and immediately think, Omigod, I need that! Before you know it, your beauty arsenal consists of toners, moisturizers, scrubs, retinols, cleansers, creams, and more. Not only is applying all of these products excessive and time-consuming, but you run the risk of irritating your skin. According to Luftman, your daily skincare routine should really cap off at three to four products. “You only need a cleanser, daily sunscreen, and a treatment-oriented product—like a moisturizer, acne treatment Dream beauty pro, or anti-aging product,” Luftman says.

If you’re constantly tempted by a new mask or cream that you bought, keep it out of sight so you only use it occasionally. And nix harsh scrubs and toners from your daily routine—they should only be used two to three times per week, Luftman says.

Mistake #2: You skimp on sleep and water  There’s a reason your face resembles a celebrity mug shot after a night of partying. “Sleep and hydration are essential for skin health,” Luftman says. Not getting enough water can literally leave your skin thirsty, making it look dry and dull, so make sure you’re drinking enough water every day (and it’s not necessarily just eight glasses!). And hitting the sheets a little earlier can help give you a healthier glow. “Sleep is so important for skin turnover and for blood volume coming to the skin,” Luftman says. “It just makes all the difference in the world.” Stay fresh-faced by aiming for the recommended 7-8 hours of sleep each night.

Mistake #3: You pick products that try to do too much When a single product promises you clearer skin, fewer wrinkles, and smaller pores, who wouldn’t want to snatch that up? The problem: It’s highly unlikely that a product will contain enough of each ingredient to live up to all of those claims—and if does, it’s probably too harsh for your skin. “Women are now tending to use products that multitask. Unfortunately, that means choosing products with more and often irritating ingredients,” Luftman says. Her suggestion: Check out the ingredient label—anything after the first three ingredients isn’t doing much. Instead, stick to products with fewer ingredients that are targeting a specific issue, says Luftman.

Mistake #4: You put on products a little haphazardly   Yes, it actually matters which products you put on first, which ones you combine, and when you apply them! When it comes to layering products, you want to put on the treatment-oriented product first, says Luftman. For example, if you’re using a retinol or acne treatment, you should apply that before a basic moisturizer. And talk to a dermatologist before using more than one product with irritating ingredients, like benzoyl peroxide or salicylic acid—two common OTC acne-fighters. Finally, use harsher products like retinols at night, since they can make your skin more sun sensitive, says Luftman search engine optimization.

Mistake #5: You leave your makeup on at the gym We know it can be a little unnerving to work out totally bare-faced, but your skin will be better for it. Even mineral makeup formulas that swear they won’t clog your pores can still cause you to break out after a sweat session, says Luftman. Keep makeup removing wipes in your gym bag so that you have no excuses. Feeling too exposed? You can get away with wearing a very basic tinted moisturizer—just make sure it’s oil free, says Luftman.

Mistake #6: You’re skipping a daily sunscreen We know you’ve heard it a million times, but it’s worth repeating: “The most important step not to miss on a daily basis is the use of an SPF,” says Luftman. Not only can it protect you against sunburns and skin cancer, but new research found that people who use a daily sunscreen with SPF 15 or higher have significantly younger-looking skin. Luftman’s suggestion: Simple’s Protecting Light Moisturizer with SPF 15, an oil-free formula that shields against UVA and UVB rays. In this case, it’s fine to let a moisturizer pull double-duty as a sunscreen (See mistake #3). If you plan to be in the sun for an extended period of time, be sure to layer on something a little stronger—like SPF 30 or higher Dream beauty pro.