One thing I've been noticing about working through a reasonably full plan of something is that, no matter how well you think you've got it planned out, no matter how much you swear that this time you'll do it by the outline that you've got, when it comes to the actual writing bit, things end up having to be changed.
Partly, that's probably because my plans are never as perfect as I think. I get the pacing wrong, or I jump about too much. They're things that I should be able to fix at the planning stage, but always look different once the words are down on the page.
Partly, it comes down to a question of creating tension/interest in each scene. Sometimes, a segment might serve the whole perfectly, but when you're talking about a thousand words or so, it has to be something as well as simply adding something, if you see what I mean.
Mostly, of course, it's because I'm inclined to get carried away. Or I figure out a great way of achieving the main goal of a scene, but it requires me to set things up further back, thus pulling things out of shape.
So, should I be doing this? Should I be improvising like this, or should I accept that plans are occasionally there to be stuck to.