As you work on a project, imagine what exactly will make it perfect, and aim for that. When you realize that your project has finally become the largest, most stylish, or most useful, you will be sure that you did everything right.
Solution: The project manager must know exactly what a successful project will be for the customer. This factor will give confidence that when the project is completed, all its performers can safely disperse.
If we haven't pointed out another project management error that you know, write about it in the comments and tell us how you can avoid it.