How it starts & when to stop

I love challenging myself and pushing myself to do new things.  It's how I started writing M/M and now I'm trying my hand at a new sub-genre of it for a submissions call.  I've written three outlines and started two stories for the submissions call, but I can't say that I'm totally excited about any of the attempts.  The stubborn part of me wants to keep trying until I hit upon an idea that will spark the motivation and momentum I need to complete the story.  However, the sensible part of me wants to stop and abandon this particular submissions call and look for another one that plays more to my strengths, i.e. something I've done before.  It's really hard for me to abandon an idea, especially given how much time and effort I've put into it already.  Then again, do I want to waste even more time on a project that may not ultimately result in a finished work?  The stubborn part of me is winning out....I'm not ready to throw in the towel yet.  :-)