Since your hair is subjected to so much heat and chemicals in a keratin treatment, they tend to be weak and malleable. To ensure that they do not get bent out of shape, you must take extra precautions like preventing tucking them behind your ears and not braid or tie your hair for at least a few days. While sleeping, you must put your hair down, so that they remain straight. You can lie on your back and keep them on your shoulders. If you see some dents after waking up, you can run a wide-toothed comb to remove any kinks, or use a flat iron for stubborn kinks. Once you are through with this post-treatment care, you can tie up your hair or sleep as you like.