Find the right time and place to write - for yourself; not just what the writing books recommend. Everyone's schedule is different, as is their writing style, so if a coffee shop isn't the best place for you, search for the one that does.
Learn to sense when you start feeling tired after a writing session, and leave things at that. And don't feel bad if you can't meet your daily quota every single time. Sometimes, scenes need time to rest and develop, and you need to approach them feeling ready and rested.
Whenever you find yourself getting drawn into a story as a reader, I think you're onto something good. Proper grammar and spelling are great, but not at the expense of flow.
