Go With the Flow.

I don’t know about other writers, but I find that inspiration can strike me at the most unexpected times.
These times are not entirely unpredictable – they’re usually periods when my mind is drifting; when I’m not thinking of anything in particular. That’s when inspiring, amazing, intriguing ideas will often bubble to the surface. If I sat down to “deliberately think”,  this burst of creativity would probably not occur. It has to be spontaneous. And when inspiration hits, it feels like such a rush! And that is when, if at all possible, it’s best to put pen to paper.
When you do, pay no heed to spelling, grammar or punctuation – just write!

Walt Whitman, the great American poet, wrote:

The secret of it all is to write in the gush, the throb, the flood, of the moment—to put things down without deliberation—without worrying about their style—without waiting for a fit time or place. I always worked that way. I took the first scrap of paper, the first doorstep, the first desk, and wrote—wrote, wrote. … By writing at the instant the very heartbeat of life is caught.

Inspiration and Discipline

Write by hand

That said, it would be impossible (for me) to write a whole book if I only wrote when inspired. The inspired writing provides the basic “clay” from which the “sculpture” can be formed. It’s disciplined writing that finesses that basic clay. Disciplined writing takes place when that bright glow of inspiration has faded and you need to make sense of it all, insert “bridges” between scenes, get rid of any cliches that may have crept in, add some description, fix the spelling, grammar and punctuation, and so on.

There’s an interesting article that touches on this topic at The Write Practice, here. It’s called “Writing Inspiration: Do You Really Need It to Write?” by Joe Bunting.