I'm here to tell you: don't do it. Slacking off can be a slippery slope. One missed deadline can lead to two. One missed critique group meeting can lead to two, can lead to three, etc. I have a lot of 'writer' friends who don't write much anymore, because they fell down this slope.
It is precisely when it's inconvenient to write that one needs to write. This is your passion, after all, isn't it?
As long as you put one word at a time down on the screen or paper followed by the next word, and so on, you'll be okay. Keep on going!