You have promised your boss that you will work some extra hours next weekend. Due to a family problem you will be unable to fulfil your promise.Write a letter of apology to your boss explaining your reasons and promising to make it up to him/her.
I wrote something. Is this alright?
Dear Mr Johnson,
Please accept my sincerest apologies for unfulfilled promise. Due to a family problem, I will be unable to do some extra work next weekend.
I must explain you why I will not be able to work next weekend. My grandfather got ill and we are going to visit him. Because my relatives live far away, I will not be at home all weekend.
I will try to do some work at home if possible. In an attempt to make it up, I could work longer this week, too.
I hope you will accept my apologies for inconvenience caused.
Yours sincerely,
Harrison (employee)

