While passionate writers love to write, writing is still considered a disciplined activity. For me, though I love to write, it's usually a problem to make myself sit down and actually start. Once I do, I could write for hours, I just need a nudge in the right direction.
I know lots of writers have this problem. Another thing is that writers are usually avid readers, and we do not always want to have to put aside our favorite fellow authors to write our own things. Reading is a great way to gain inspiration--I go on reading spurts when I'm pondering what to write next, and usually I come back fresh and ready to go on with whatever I'm working on. But you should not let reading, or anything else for that matter, get in the way of your writing career. It makes for very angry muses, and a disruptive character purgatory, and that's never a good thing. If your characters are angry at you for neglecting them, then put down that new (name your favorite author here) novel and get to work!
Another thing that can be a problem is having company at your house--you know, out of town family. For some reason I always HAVE to write when there are visitors around. This can put a damper on things, but that doesn't mean you can't skip off to a corner and write a little bit.
Laziness is never a good excuse. I'm sorry, you're just not going to get out of it! If your characters are trying to kick you out of your chair and get you to working again, then you need to listen to them. The words might not be so quick to come the next time!
Here's some things that help motivate me: First of all, don't feel bad about treating yourself. This could be as simple as buying yourself a candy bar, or, my personal favorite, Pringles! And then putting them away until you finish what you were supposed to. The reward system is not just for children, you know. You can either do this, or have a special "writing time treat" like a delicious latte or snack that you only eat when you write. Mine is cherry sours. I'm eating them right now...
Setting goals for yourself is good too. And helps with the rewarding... I challenge myself to at least write something everyday. Whether it's for a novel I'm working on, a short story, or a blog post, or just something fun. If you're at a loss, look up some writing exercises on line that you can do. I've found some pretty fun things. I also like to write silly humor pieces or spoofs for my own books or my favorite books; even if you never intend anyone else to read these things, it's good to keep writing.
If you like to write with music, then putting on something that will set the scene is a great thing to do. I have different favorites for whatever I feel like writing. Sometimes, I just listen to music and then I get ideas for what to write. I am always very inspired by music.
Have any other tips you would like to share? Tell me about them in the comments! I'd love to hear from my fellow writers =)