I used to straighten my wavy/curly hair every day and it got really dried out. Get regular trims and invest in a good conditioner. (I like Neutrogena’s deep therapy stuff. Not too expensive, and really, really good). You can also use leave in heat-protectors. Aveda’s Glossing Straightener is really nice. I recently did a dramatic color change and my hair got seriously fried. I only shampoo 3–4x a week now, condition on most of the off-days, and don’t straighten it daily. I’m amazed how much healthier it is.