Okay, I am going to share my secret for finishing. I discovered this late, but am glad I did. Are you ready for it? The secret is this: don't start something till you finish the last thing, no matter how poorly. This goes even at a "micro" level, so don't start distributing the load on servers till you finish the last thing (interface), no matter how poorly you finish the last thing. Now you have the secret. Go forth…
Totally agree, my mantra is "The enemy of my main project is all the other projects." Starting is fun and seductive, finishing is a grind, but boy does it feel good when you do. It's how I finished a novel, a massive YouTube project, an iPhone game, etc.
I first "discovered" this trick with writing myself.