Laws of Project Management

Rule 1: No major project is ever installed on time, within budget, with the same staff that started it. Yours will not be the first.Rule 2: Projects progress quickly until they become 90 percent complete; they then remain at 90 percent complete forever.Rule 3: One advantage of fuzzy project objectives is that they let you avoid the embarrassment of estimating the corresponding costs.

• When things are going well, something will go wrong.
  
• When things just can’t get any worse, they will.
  
• When things appear to be going better, you have overlooked something.
  

Rule 4: If project content is allowed to change freely, the rate of change will exceed the rate of progress.Rule 5: No system is ever completely debugged: Attempts to debug a system inevitably introduce new bugs that are even harder to find.Rule 6: A carelessly planned project will take three times longer to complete than expected, a carefully planned project will take only twice as long.

Got these laws here