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Mistake #2: You get weekly blow-outs.
We hear you: The rapid expansion of blow-dry bars is pretty great. But it's easy to get hooked, especially when the salons offer hard-to-resist, money-saving packages. Regularly exposing your hair to high heat via dryers, flatirons or curling irons isn't healthy for your hair at any age, because it creates air bubbles within the hair shaft that make individual hairs more prone to breakage, and the longer you do it, the worse it is. Amiel says repetitive styling methods definitely weaken hair. After awhile you'll likely notice that your hair looks thinner or that strands break more easily than they used to. Take some time off from regular blow-outs and let your hair air dry sometimes; and if you do use heat, try to stick to the medium setting (which is usually around 200 degrees).