Too much of a thing is never good. Take hot tools as an example, they are great for styling, taming and making hair look and feel great, however using them too much can increase the chance of heat damage. 

Over time as high heat is applied to the hair, it strips the hair’s natural oils resulting in the water molecules evaporating and altering the hair’s natural protein structure from A-keratin to B-keratin, which leads to weaker hair that is more prone to damage. This occurs with exposure to temperatures over 300 F, which many hot tool temperatures exceed.