Avoid asking irrelevant questions about the past that will be annoying to others. If someone keeps complaining to you about the past, ask him, "What can presently be done about it? If nothing, isn't it better to focus on other things?" If the other person persists on talking about the past, weigh the situation. At times you might be doing someone an act of kindness by listening to him. In other circumstances you are better off ignoring statements about the past and thus teaching the other person it is not worthwhile to discuss with you something which is over and done with.