It's an old saying, and perhaps a cliche one... "Follow your gut", or "trust your gut".
I find it interesting that the more you write, the more you can do just that.
I can recall early on in my screenwriting, when I'd hem and haw about this or that - taking considerable time (and energy) to make sure that a character name was just right, right off the bat. To get a line of dialogue perfect the first time. Obviously, subsequent drafts (beyond that original vomit draft) will fix a lot of the problems and hopefully confirm (or deny) choices already put to paper.
But as I continue in this writing journey, I find myself - multiple times a day - making a swift judgment call and simply moving on. It can be in a piece of description, a decision on whether a line of dialogue should begin with "Well...". So many little things (not inconsequential, mind you) that, once upon a time, I'd have lingered on and frankly, wasted valuable time.
I hate to sound like an ass, but some of these things now feel like second nature to me. An instinct. And that's a good thing.
Sure, I have plenty of moments where I'll pause and hash something out - perhaps because it requires such intense thought. Does this character die? If so, how does it have an effect on the lead character? Things like that do need some time to simmer...
It's also interesting to note that during face-to-face feedback with my own beloved script editor/story consultant, we'll whip around ideas on an already 3-drafts in script. And when certain suggestions come up, it takes but a look up to the muse in the sky and a moment of thought before arriving at an almost immediate "yes" or "no". That's a moment of trusting your gut, thoroughly knowing your story and your characters, and realizing immediately that it will or won't work. And it wastes no time.
Things that require further discussion, by all means, get in there and dig for a conclusion.
I'd love to see the statistics on my own writing, about how many times these now-so-common "split-second" writing decisions, ended up staying exactly the same when eventually clicking "save" on that final draft.
The point I'm making, is that if something comes to you quickly and it feels right - do it. Get it down on paper. Follow your gut.
I mean, it can always be changed later, right?
(not that you'll need to if you follow your gut).