Using too much heat (curling and flat irons) damages your hair. The best way to prevent this is by using a heat protectant and only taking the curling or flat iron (especially) through your hair once and not twice or more. Also when using a flat iron, also use a comb to run behind the flat iron as you pull down. That way, you know your hair isn’t tangled, etc.
Using Harsh Shampoos
There are many ingredients in hair care products that are harmful to us and we don’t even know it. It smells great and we immediately fall in love with it (especially when its achieving the look that we want) and though that’s fab, it isn't best.