[Your letterhead, if desired; if not, your return address]
[Date of letter—month, day, and year]
[Recipient's first and last names]
[Street or P.O. box address]
[City, State ZIP code]
Dear [recipient's name]:
I just want to let you know how sorry I am for missing the date we had set up for today. It was "one of those days," and my workday was much busier than expected. Also, I had some car troubles this morning so was dealing with that. I know I called you to let you know that I would need to cancel our date, but I just wanted to send you a note too. I was really looking forward to seeing you again today and was disappointed about having to miss our date.
I would love to get together with you sometime soon. Just let me know whether you are available this weekend, and if so, what day and time work with your schedule. I look forward to seeing you really soon, and thanks for being so understanding about me needing to change plans.
[Sender's first and last names]