There will always be something else to do other than write. Many other things; some of them even important. It makes setting time aside to write harder--but no less necessary.
It may seem strange to think of writing as a "necessary" thing to do, but for those of us who just can't ignore the urge, it certainly is. I'm not sure what I expect to get out of my writing, or if I expect anything. All I know is that I am happier when I am writing something. I feel a sense of purpose and accomplishment that very few other things can provide. This means it is worth pursuing. And, yes, even necessary.
I believe this is the first step toward finding the time to write--allowing yourself to believe that it is a necessary part of your life. Allowing yourself to believe that it is important. Once you convince yourself of these things, it becomes a little easier. A little. There will always be those other things that loom over you and demand your attention. But that's when you squeeze in those tiny, little moments to yourself, to sit in front of your computer or your notebook and write.
Because if you do, you will find yourself filling your life with little moments of purpose and accomplishment--and you will be happier for it.