My solution to this (same as my solution to a lot of things, really) was to make a spreadsheet and set a goal for myself. The spreadsheet is really simple: Across the top are the days of the month. Down the side, are a list of my current stories (some of my current stories, I should say; I have some to add) and a space for new work. In the remaining spaces will be my word count, IE the total word count for each of the stories and the total word count for each day. The goal I set is also really simple. I will write a minimum of 1000 words per day and at least 500 of those have to be on an existing story. The rest can be spread amongst anything, other existing stories, new material, blog entries, etc.*
Because I'm a nerd, what I'm most excited about is being able to track my progress through the graphs which I will periodically make. I'm hoping this will give me the motivation I need to get back on the writing track. My other (not as good) solution is to resort to Redbull and gin, and see where that gets me. At the moment, I'm thinking graphs are a better idea
*Yes, this counts. I've just upped today's word count by 286 :)
Edit: I wrote this on May 1st. Since then, I should have written almost 3000 words, and I'm sitting at just over 700. Shame does not begin to describe it. Anyway, should get cracking; I have a lot of catching up to do.