1. I didn't write this in the thick of the battle -- I've already had 2 weeks with most of my responsibilities lifted. This is what's given me the presence of mind to write what I have. Also, the more 'down' I am feeling, the more I tend to write. Writing my thoughts comes naturally to me -- it isn't correlated with motivation or mood or anything of that sort.
2. I think advice on tactical stuff like achieving tiny goals daily can actually be detrimental to a person who's beyond a certain point of burnout, because these little changes can distract you from bigger issues that require bigger solutions. Don't get me wrong though, I appreciate what you're saying and I tried ideas just like you've described for weeks before finally realizing where I was at and talking it over with a mentor (who recommended that I act -- fast -- to prevent further degradation).
3. Maybe what you're sensing is that I still really do want to be successful in life -- because I most definitely do. But as for this business, in reality it requires my 100% commitment before it can budge another inch, because we have some big spending humps coming up and if I can't predict with certainty when I'll be back in the game in full force, it's too risky to front more cash right now... and right now all I can think about are the blue skies I need to be staring at while I take a real break, and how intensely awful this has been on my mind and body and how bad it would be to have it continue, now or in the future. So while on some level I do want this business to be successful, I would have a very hard time committing 100% to be available again at a certain, and fairly soon, date. I think that would be too risky for me, and for the investor.
There is some excellent feedback in this thread. Let me add mine, which may be a little different. I go through what you are experiencing all the time. There are days when I can't stay awake at my terminal. Sometimes I hit a road block and wonder how I'll ever get by. I usually step away for a time, but here is my real secret...
Pick one little thing that needs to get done, no matter how small or unimportant it may seem. If I'm really down, I pick some mundane task like refactoring 25 lines of code, manually updating 50 records, or even changing some naming conventions. But not something big like solving a client-server architecture problem. Hell, that's the reason I'm already down. One other thing - the task must be in the heart of your project; cleaning off your desk or reading a journal don't count. Then do the task. Completely. You'll feel a little better, I promise. The next day, do it again, maybe with a slightly bigger task. And again. And again. Who knows, you may be feeling a lot better before you know it.
I have no idea if my advice can help save your project, but I do know you still want to. Use this group for support (I know I already do) and keep us posted. You are not alone.