First of all- writing a project of any length takes patience to actually sit down and get it done. Some people write it out in notebooks, most type, and a few dictate while running errands or working around the house so they can go back on their computer and edit at a later date.
Patience is important during the actual writing process because rushing will make your work sloppy and hurried. There's nothing wrong with taking your time. I've heard of authors finishing whole manuscripts in 72 hours...this is not for everyone. You're not running a marathon!
Patience is also important after the manuscript is done. Unless you're in a serious time crunch, or you really trust (or maybe want to torture) your Beta readers, it's best to leave the manuscript alone for a couple of weeks. That way, you can pick it up again with fresh eyes and read through it again. It's easy to skim over mistakes or leave loose ends untied after you've read through the same chapters several times in a day.
I really don't recommend submitting a manuscript to publication immediately after you write it. It's better to self edit as much as you can before you send it off to the professionals. Make an effort to put your best foot forward and all that.