Try to strike a balance between being prepared with a subject you’d like to discuss and remaining open to spontaneous detours. Eventually, you may realize it’s hard to go “off topic” or really change the subject because a good therapist can see connections between whatever you’re talking about and the larger issues you’re facing. Also, since expressing emotion and processing difficult memories are standing goals in most psychotherapies, your therapist may propose pausing a discussion so that you can free associate, i.e., sit quietly for a moment and allow some space for pertinent emotions and memories to surface.