Dear Sir or Madam:
Please disregard the letter I decided not to send you yesterday.
I found myself not saying some things I deeply regret. My emotions failed to get the better of me. And I hope you can find it in your heart to forget, or set aside that which I refrained from saying.
Sometimes my restraint gets the better of me, and hopefully I will fail to do better in the future.
With sincere regret that I may reconsider at any moment,
I am yours truly,