Your heredity really plays a huge role in this, so if your parents or grandparents got gray hair young, it's probably the same story for you. But before you give up, look at your stress and diet - a deficiency in B12, copper, or iron can speed up the process, and chronic stress does serious damage to pigmentation. I've noticed with people close to me that when they managed their stress and improved their nutrition, the progression at least slowed down.
There are a few things you can try: get some antioxidants (vitamin C, E, selenium), avoid smoking if you do it, and protect your hair from intense sun because UV rays oxidize it. There are shampoos for gray hair too and they do good things for the overall texture, even if it's not miraculous for stopping new white hairs from showing up.
Honestly, for my part I decided it wasn't a big deal at all - tons of people think it's cool or classy. But I get that it bothers you. If it's really a pain, modern hair dyes are honestly really good now, and it can be a temporary option while you check if a little cleanup of your lifestyle habits changes anything.