The same work under the same conditions will be estimated differently by ten different estimators or by one estimator at ten different times.
Any project can be estimated accurately (once it's completed).
The most valuable and least used WORD in a project manager's vocabulary is "NO".
The most valuable and least used PHRASE in a project manager's vocabulary is "I don't know".
Nothing is impossible for the person who doesn't have to do it.
You can con a sucker into committing to an impossible deadline, but you cannot con him into meeting it.
At the heart of every large project is a small project trying to get out.
If you don't stand for something, you'll fall for anything.
The more desperate the situation the more optimistic the situatee.