I am writing to apologize for the mismanagement of [project/task/etc.]. I understand that this has caused a great deal of frustration and inconvenience for you and your team, and I want to express my sincere regret for the situation.
I take full responsibility for the mismanagement of this project. I failed to properly plan and organize the project, and I failed to communicate effectively with you and your team. I understand that this has caused a significant disruption to your workflow, and I am deeply sorry for the disruption.
I have taken steps to ensure that this type of mismanagement does not happen again. I have reviewed the project and identified the areas where I could have done better. I have also implemented a new project management system that will help me better plan and organize projects in the future.
I understand that this apology may not be enough to make up for the disruption caused by my mismanagement. I want to assure you that I take this situation very seriously, and I am committed to ensuring that it does not happen again.
Once again, I apologize for the mismanagement of this project. I understand that this has caused a great deal of frustration and inconvenience, and I am deeply sorry for the disruption.