Think of something you've done in the past, and write a note of apology.
Here are some ideas for your letter:
• A problem you had with a neighbor
• Saying something that you later regretted
• A time you upset someone without realizing it
• Being responsible for damaging something
Check that you use expressions like these in your letter:
• I just wanted to say I'm sorry for (not) . . . -ing
• I would like to apologize for . . .
• I feel I should apologize for . . .
• I promise not to . . . again.
• It was my fault entirely.