Hello Jason, interesting though ^^
I, as many if us, had to deal with this kind of things but I found something very useful in this process : a team.
I don’t say that you have be part of a big team but if you work on your project with 2 or 3 other people, it changes everything !
When one of us are tired / demotivated / bored / unsecured, the other can help him to go through these bad times.
Seeing other people works is a great motivation !
How can I be the lazy one while the sound designer just made this great music ?
I can’t sleep while the animator wait for my rig to work with…
I did the cycle you describe many times but now, I work with some friend and I feel immune to it 
Even if I still the main worker on my project and spend much more time on it than every one else, the fact I involve other ones on my project forces me (in the good way) to work every day.
BTW : He propose a much complex equation than yours (seven unknown !) but his point is really interesting :
