I have a few times, I think of an amazing idea which then slows down and i think of it as standard but with a twist. The actual idea is still pretty good to everyone elkse, but not to me and that is mainly because of what you said in your post Bigace. I start off good, but then run dry of time, patiance, inspiration and overall interest to the game/ project i'm working on.
It's only recently that I've stuck to my project, obviosuly other factors have kept me at bay, for example university courses, jobs, socialising etc but it's feedback and comments made to your project which keeps me moving and motivated. Eeven if it's 1 individual leaving feedback, that's all I need to keep going, just for someone to recognise my work.
One key factor that inspires me is music, music is endless, new pieces can be released so in theory I can keep hearing new music that could inspire me.