Think of a time when you trusted someone and should not have. For example, you might have told a friend a secret and then the friend blabbed it around town. The resolution might have been that you realized that person was not your friend after all.
The plot for your anecdote would be the story of the event. Think about a time when you said something you shouldn't have - a time when you told a secret to someone who wasn't supposed to know the information, a time when you said something that hurt someone's feelings without you meaning to do so, a time when you spoiled a surprise event for someone else because of something you said.
Your anecdote would start with explaining the situation, which is the setting and introduction of the characters for your story. The rising action would be the events leading up to your unfortunate statement and the reaction to it, which would be the climax. The falling action would tell how you corrected the hurt or made up for the mistake you committed. Your conclusion would be a statement of your resolution never to repeat whatever it was that turned out to be the mistake you made.