My suggestion would be to create a writing schedule and adhere to it as much as possible. I believe that rushing to write is too stressful and disheartening.
An even more important schedule is your sleep schedule. Not sleeping the full 8 hours and/or going to bed at different times everynight leaves you tired for the next day.
Finally, before writing the chapters themselves, write an outline of where you want your story to go, as well as a glossary with all of your importannt characters, their motivations, and some basic info. This may sound constraining but it's quite the opposite. Having a clear direction beforehand helps you stay focused on the writing itself, and being familiar with your own characters allows you to quickly write how they'll act, without the need to stop every thirty seconds to think about it.