Don't look at your situation as a bad thing, it gives you the opportunity to step back and evaluate, what, how, when and if you want to continue. As a metal fabricator building race cars and street rods, I work daily with challenging projects. Sometimes I am building from a simple idea in my head or with a CAD drawing. I build scale plastic models as well, some from kits, most from scratch, and of course pepping Halo stuff. What do all these share in common, some days you have a pile of debris on the shop floor or work table and little progress to show for your efforts, frustrating, yes, a motivation killer sometimes.
A friend taught me long ago that when a project turns out in a less than desired outcome to look at it as a result, not a success, not a failure. A result is a learning! With every success or failure you take something away from it, those learning build your skills, those increased skills will allow you the chance to change your focus/mindset and challenge yourself
What ever your chosen project, build for yourself! In the plastic model world I have from time to time been confronted by those I call the accuracy police, these types will wander around the contest hall eagerly pointing out all the short comings of other builders, "that colour is two shades dark, that panel line is to deep, etc."I could tell your how I deal with those types but my goal here is not to get barred from the 405th.It suffices to say, if the get as much enjoyment from doing that as I did building for me, then we both have satisfied or selves.
I have found as well whether building with plastic, metal or foam and paper, breaking down the builds into sub assemblies and providing yourself with multiple projects of same or different media will help from getting stuck in an area of a build that is going nowhere. It doesn't take long to spend hours of zero productivity staring at a project that is not going well, when simply side tracking yourself with a change of scenery, a different component will refresh and recharge you
Enough of my ramble, build, enjoy, and share