Many patients leave psychotherapy although in need. What can professional practitioners and researchers assume what happened? Trying to receive a response from these patients we too often are left without an answer. In this paper I introduce to psychotherapy discourse some concepts taken from linguistics and Conversation Analysis (CA). The reason is that what psychotherapists of every kind do is “talk-in-interaction”. During such talk Typical Problematic Situations (TPS) appear which are well known in a macro-analytic perspective (if a patient comes late to the session, does not talk or blackmails the therapist with suicide threat). However, there are many TPS that can be detected by a micro-analytic perspective only. CA is a tool helping to idenfity this type of TPS. One relevant CA-concept is Common Ground, a psychological and linguistic concept which requires special activity from both participants in an interaction. Conversational “errors” that risk to tear the Common Ground often go unnoticed. Presenting segments of transcribed therapy sessions I want to direct attention to the details of how ‘errors’ in Common Ground activity happen, how they are noticed and dealt with by skillfull therapists or how they can become repaired. Among others I use transcription details of two suicidal patients. The transcripts are from the CEMPP-Project (Conversation analysis of Empathy in psychotherapy process), conducted at IPU, Berlin. Thanks to a grant by Köhler-Stiftung, Germany.