Did you know that you can lose around 80 to 100 hairs per day?
Have you seen them in your hairbrush? It is part of the normal hair growth cycle which determines that each hair will grow for so long (between 2 and 7 years) and then fall out. Then another will grow in its place. All the hairs on your head are at different stages in the cycle.
This is why some people cannot grow their hair to a very long length, their hair growth cycle does not allow their hair to grow for many years.