Another way that writers prevent themselves from completing a first draft of a project is by chasing things that are a) moving unpredictably or b) new and more interesting by virtue of being new.
Chasing the market is when you start paying attention to what everyone else is doing/writing/selling and the ambitious side of you adopts the seductive idea that if you write towards trends that you’ll have a better chance of producing publishable material that people will want to represent or buy. The problem with such a strategy is that by the time you are hearing about a trend, the trend is either already changing or there are writers out there who have completed drafts of work that speak directly to the trend. You also might want to consider whether or not you have a genuine interest or accrued knowledge about the trend in question. The bottom line here is that if you stop work on something that you’ve made real progress on in order to write to a trend, you are killing a project before you’ve given it a fair shake. Finish the thing you started.
Consider why you were drawn to writing fiction in the first place. For most of us, it’s because we fell in love with stories and wanted to start telling our own. I’m not saying that in the process of creation you will love every minute of it, but do the thing that personally as a reader and a writer excites you. Check trends when you have something finished and see if the finished piece matches. Chances are you will, by virtue of talking to readers and writers, be aware of trends already, regardless of whether or not you happen to be tracking them.
There are many roads to publication, but crafting with trends at the forefront instead of placing the story at the forefront is a good way to keep you second guessing yourself, and to keep you from finishing. This is one of those areas that I advise trying to compartmentalize. When you are working on fiction, work on the fiction, and if you have to, carve out some time to stay updated on the publishing world and consider your goals. Do not let that distract you from making progress on the work. You have to put the work first or none of the other information about publishing will matter. Keep in mind I am talking specifically about first drafts for novels. Things with short stories can be a bit different with calls out for themed anthologies. Do it if the theme and genre excite you, don’t just do it to be mercenary about submitting to as many places as possible.
The second thing I think is one that we all, at some point, fall prey to: the shiny new idea that hits you just as you are gaining momentum on a project. I think this happens to every writer. We’ll be working on a piece and then something tangential to the main story will suddenly grab hold of our imagination and give birth to a new idea. Because the new idea is new, unexplored territory and we haven’t hit the point where that new thing feels like work, sometimes we’re tempted to chase it in favor of the thing we’re working on. The advice here is not to disregard the shiny new idea, but to write it down and come back to consider it later.
Something that has started to happen for me, when I put that into practice, is that while I’m working on the current draft the new idea sort of percolates when I’m doing other things not related to writing. Details about the new idea will arrive when I’m at the day job or doing daily household maintenance. It doesn’t hurt to write those down when they arrive, but keep working on the current project, and hang on to those notes. The notes for the shiny new idea will help give you direction when the current project is done and you can dive right into the next first draft when it is time to let the current project sit for a few days or weeks which will enable the critical distance needed for editing. Doing this instead of abandoning the current project is a habit that will help you maintain momentum in writing fiction. It also prevents you from scrambling for ideas on the next project because you’ll already have something you can build on.