Never, ever (but absolutely never!) try to write a software proposal without first having had meetings with the customer/client/boss/department/whatever in which you described by words and face-to-face much of the little things that will define your project.
And if by any chance you are caught in a bind like I was and have no choice but to write the damn 30 page wall of text explaining every little thing the program will do (not to mention you will still need to write the development contract), don't be a greedy bastard like I was and simply refuse to go on without first having those meetings.
I'm on the 4th day of writing this #"#$@ proposal and I think I had my share of Word and Visio for the rest of my life. I'm tired, I want to cry, my eyes hurt and I feel like I'm stupid.
So... don't do it. You gonna regret it. Badly.
Everything is easy when we were just thinking about it. Think about it.