On a roll?

I've spent the last week reading round an idea for a new piece. I'll be collaborating with a friend and now we've got to the point when we think can take the idea to a meeting with some confidence that we can make it stand up. In other words if we do any more work on it we'll be in deep and there's no point in continuing if it's not going to be commissioned.
I've found it increasingly difficult to work on something that hasn't been commissioned. When I was trying to get out of the slush pile I did it all the time, but then I was only hoping to have someone read it, I never seriously believed that any of my work would get produced, I knew they were calling cards. I got GFA money the other year to develop and write a play and it's not bad, people like it, it's got me work, but it hasn't found a production. I can't bear to put all that graft in if it's not going to be produced. I do write all the time though around ideas I've got to see how they might play out, but that's not the same as committing myself to a complete play with no sign of interest.
Now, because I've got an unexpected gap thanks to Hannover, I am working on an idea I've had knocking around for a time and I keep returning to it and I think each time I do it gets simpler and therefore better. The other day I worked on it morning and afternoon and then when I was on my own in the evening instead of falling in front of the TV for some aimless channel hopping I went back upstairs and carried on. I feel as though I'm on a roll, but it could be an illusion. Again.