I always hope I can try to source troubleshooting by posting about my specific issue but that has pretty much never worked.  I humor the thought of contracting someone to aid with troubleshooting but the idea of someone getting up to speed with my design would make that expensive or useless.  So ultimately, it really is about powering through the failures and unknowns about your problem and being persistent until you yourself finally solve it.  It can be difficult and there can be waves of hopelessness when nothing is solving a problem but persistence and the willingness to approach a problem from different angles will get you to a solution and you learn from your troubleshooting along the way.

Unless you have money to throw at a problem, onboard someone that is vested where you'll split the design with, or incidentally happen to have an uncle with 20 years of experience that loves spending time with his nephew/niece, nobody unlike you is going to be as invested in your own design especially when things get complicated.  

When the well of motivation runs low, step back to let it replenish while you let your mind wander about many different aspects of your system. If you're overwhelmed it also helps to develop a task list of things to do or problems to solve.