Everyone makes mistakes, and even though people do their best to act professionally in a business environment, it is possible to lose control and say something or do something that you regret later.
When you let a certain action or happening cloud your vision, you might act out of instinct and suddenly forget your place.
The most important action to take if you have done something that you regret is to write and apology letter. Such letters can be written to colleges, co workers and your boss as well. A well written and sincere apology letter can make everything go back to normal.
In an apology letter it is essential to assume responsibility for what happened. Do not accuse and do not try to look for excuses. You don't need to put blame on something or someone else, you simply need to be responsible and offer to make everything better.
An apology letter can be written in case of hurt feelings, damage that you caused, false accusations, bad service and so on.
Dear Dr. Marks,
I am writing to apologize for my behavior during our meeting last Wednesday. The manner in which I spoke to you was not only unprofessional, but also completely without any justification.
I've been your employee for 3 years now, during which I have grown to admire you and respect you for the great job and insight you have. When you decided to use a another program than what I have been accustomed to, I reacted right away without thinking and judged you for your decision. It was wrong of me to do so. It is not my place to make a judgment like that.
I should have waited to talk to you in person about the matter and not in front of everyone else. In the same time, it is not my place to judge your decisions.
I would like you to know that I accept full responsibility for everything that happened and that I would like you to accept my sincerest apologies.