Let me start by saying that this is how I feel when I know it's time to write a query or synopsis:
BUT, as all writers know, they are a necessary evil. I've always attempted to draft a synopsis before tackling the first draft - it helps keep me focused on the major plot points, and I can identify any fatal structural problems before I begin. One time I also drafted my query before writing, but it was for a WIP I have for the moment lost interest in. However, I am totally in favour of attempting both a synopsis and query before drafting.
Right now, I'm in the middle of a rewrite. I originally *hoped* this latest manuscript wouldn't need it, but I can't deny my 'writery' instinct. It needs work. Substantial structural changes, in fact. It has the right heart, but it lacks...too many other things. So I decided I was going to get serious about keeping myself on track. I took the bold step of writing a synopsis of all the major plot points, which I'm filling in with other developments as I draft. I have a timeline, and also all of my major plot and character arcs written down. And as much as I hate writing them, I spent quite a bit of time drafting a query letter. It's by no means perfect - I am definitely not the best at queries - but it serves a really important purpose.
It's keeping me interested in what I'm writing. I actually love my new query. It'll no doubt get ripped apart and stitched back together when I start getting it critiqued, but all the elements that make me love this manuscript are in it. Rewriting is draining, and it would be easier to shelve this manuscript and turn my hand to any one of the other little plot bunnies harassing my brain. But I don't want to do that now.
So whenever I get stuck on a scene, or have a moment of weakness, I can look back at the query and think YES. This is why I want to tell this story, and I WILL tell it. I also have an - admittedly flaky - pitch crafted, which I can tweak and polish as I go. When this manuscript is ready to query, I already have the foundations for my submission package.
Give it a go - cramming a 60-100k manuscript into a little query and synopsis is far less daunting when your mind isn't cluttered by what you've drafted. Write down the core of your book, remind yourself of it constantly, and you won't forget it even when you're drowning in subplots and line edits ;)