More on stopping, plus some comments here on matociquala's LJ
I actually just stop when I stop. I usually have to stop for external reasons anyway, e.g. it's time to make dinner or the students are about to arrive for the evening class. If I can, I do try to avoid stopping at a point where there's any sense of closure as it can be hell to get going again in that case. This doesn't necessarily mean that I'll avoid chapter ends, but I do avoid deliberately writing on to a "natural" break point and will usually stop while I still know what I was going to write next.
This idea seems to really irritate some people, while I find it useful, so it's obviously a case of YMMV. One of the things I do like about rec.arts.sf.composition is the group's very strong belief that there is no One True Way to write. I suspect that the advice to break off while you still have some ideas in hand arose because the intuitive thing to do is to write on to a scene end or chapter end and this was causing problems for some people. If you don't have problems getting going again after a natural break point, then the advice isn't for you.
One thing that's really going to affect whether this advice makes sense or not is how many words you normally write in a session. misia says she writes 6-12 pages. (Don't know whether that's single or double-spaced, but we're probably talking a minimum of 1800 words up to 3600 in a session. More if it was single-spaced pages she meant.) Anyone writing this much at a time can sensibly choose to stop at a chapter or scene end. But my target is a mere 400 words per day and I don't always manage this. So unless I'm going to write very tiny scenes, I'm going to have to stop mid-scene most of the time, whether I like it or not.
But actually it doesn't bother me. This may be a product of how I came to write in the first place. My writing arose out of all the daydreaming I did as a child and adolescent. I used to walk to school (20 minutes each way) on autopilot while running daydreams in my head. But I didn't just run these daydreams once; no, I used to have favourites that I could repeat. I would also polish a daydream, backing up and revising a scene until I was happy with it and only then going on to work on the next scene. And these daydreams were long. It could take a couple of days of walking to and from school to run through one in its entirety, dropping it when I reached my destination and picking it up again when I set off walking again. So, over the years, it seems that I trained my brain to create stories in this manner. After a while, I decided some of the less derivative daydreams were worth writing down (I was wrong, but it was good practice for later). This, therefore, is how I started writing: creating stories in my head and only finally committing them to paper when they were pretty well worked out. In this way I planned and wrote all the novels I've written up to now. (I still find that going for a walk is a marvellous way to work out what happens next.) It isn't how I'm writing this one, and another day I might talk about what I'm doing different this time. But this is why I like to find out how other writers write because one day a story will come along that won't work with my usual methods and then I'll need to try something different.
In case anyone's interested...
This is where I stopped yesterday.
Wil had gone to ground behind a couple of the tumbled packing cases. He had been cowering there with his hands over his head, but now he peeped around the side, and saw, to his horror, a band of mounted militia charging into the fray. To arrive so promptly, they must have been called out when the band of vengeful men had left the square. Whether someone wanted to protect the Earth Mages or whether they were trying to keep their men from serious trouble, he didn't know.
And then he saw Master Patticlus, bleeding from a gash on his head, go reeling past.
Ah, Goorgy! Heel, boy!" he called to the wolf.
That last sentence is a complete non-sequitur because it isn't what Wil says at all and really belongs further on, but I put it there to jog my memory about how the scene carries on from that point. I often do that if a scene is really flowing and I have to stop, I jot down a few key phrases of what happens next, which helps me get back into the scene.
When I start to write again, I just read over the last few sentences to get back into it and then carry on. You have to bear in mind that this is just zeroth or very scrappy first draft, so all the smoothing out will come at the first revision pass. Of course I have the same problem there too in that I have to revise small chunks at a time but a) I revise faster than I create brand new words and b) the chances of the break points coming at the same place are small, so any noticeable joins should get polished out.
This is how I picked up the thread today.
And then he saw Master Patticlus, bleeding from a gash on his head, go reeling past. "Oh, bugger," Wil muttered as Patticlus wobbled dangerously close to the trampling hooves and swinging rump of one of the militia horses. "Watch out, Master Patticlus!" he yelled, darting out from his hiding place and grabbing the grocer by the elbow.
[Words snipped in which Gillom (neighbour's son) escapes from the crush and manages to get to his transport.]
"Gillom!" Wil shouted as the young farmer leapt up into the driving seat and seized the reins. "Take Master Patticlus, please! He's hurt!"
Gillom turned, seemed to size up the situation in an instant and brought the dog-cart alongside. As Wil boosted Patticlus from behind, he reached down a brawny arm and pulled the grocer up onto the seat alongside him. "You coming too?" he asked Wil.
"No, I'll be all right. Just get him home, will you?"
A grin flashed across Gillom's face. "That I will!" Then the young farmer stood up in the cart, surveying the struggle that had lessoned somewhat now many of the townsmen had stopped fighting and were standing in a shame-faced huddle guarded by half a dozen of the militia. "Now where has he got to?" he muttered.
Something grey dodged between the horses, sending them shying away, almost unseating their riders. "Ah, there he is... Hey! Goorgy! Heel, boy!" Gillom called.
Tongue lolling, a silly grin on his face, the wolf jumped into the back of the cart.