It is all too easy in a discussion to raise other issues which are not...
It is all too easy in a discussion to raise other issues which are not part of what is being discussed. Often the new topic is related to the one being discussed, but is one which the person who changed the subject feels more strongly about, or feels that they have a better chance of arguing successfully. The problem is that the other partner, the one who wanted to continue talking about the original topic, may feel aggrieved about being cut short, and this resentment will prevent a good discussion from continuing. The discussion about the original topic should ideally continue until both partners are satisfied that it has been resolved, or the timer signals the end of the discussion.