Dear [Name],
I am writing to apologize for my inadequate effort in [task]. I understand that my lack of effort has caused you to be disappointed in me and I take full responsibility for my actions.
I want to start by saying that I am truly sorry for not putting in the effort that was expected of me. I understand that I let you down and I regret not meeting the standards that were set for me. I should have taken the task more seriously and put in the necessary effort to ensure that it was completed to the best of my abilities.
I want to assure you that this will not happen again. I have learned from my mistake and I am now more aware of the importance of putting in the effort that is expected of me. I will take the necessary steps to ensure that I am meeting the standards that are set for me in the future.
I understand that my lack of effort has caused you to be disappointed in me and I want to make it up to you. I am willing to do whatever it takes to make sure that I am meeting the expectations that are set for me. I am also willing to work extra hard to make sure that I am completing tasks to the best of my abilities.
Once again, I apologize for my inadequate effort and I want to assure you that this will not happen again. I understand the importance of meeting the expectations that are set for me and I am willing to do whatever it takes to make sure that I am meeting those standards.
Sincerely,
[Your Name]