I've shared this tip before, but I find it to be sound advice to the point that I'm about to put it out there again.
To those writers who find they never quite have time to get anything down on paper, I submit to you that any amount of time you spend on your craft, no matter how insignificant, is still an accomplishment. There's no shame in nickel and dimeing, especially if your willingness to work at all is on the line. It's easy to sink into the assumption that if you only have half an hour a day to write its not worth your time, and you might as well wait until tomorrow. Then tomorrow comes, the weekend comes, vacation comes, and you find that by Christmas you're still right where you started, justifying why only a little time is not enough.
Do you like coffee or tea? I'm partial to Earl Grey myself. No matter how busy your day is, I find it somewhat difficult to accept the fact that you have so little time on your hands that you can't at least sit down to a cup of your choice and the paper (or tablet as the case may be) once a day. If you're so tied up with life that you don't even have time to drink something, that's an entirely different issue. Use that cup as your timer, and instead of whatever you normally do while enjoying your drink, write. When the drink is finished, so are you.
It may not seem like much, but even if it's fifty words (or just a brainstorming session), at least you accomplished something today. That goes a long way towards keeping your eye on the prize and your head in the game. A project never worked on will only fade away.