It is important for a clinician to be emotionally interested, but not emotionally invested in his or her clients. There is an important distinction here that must be mentioned in order to further the point. A clinician who is emotionally invested in clients ties a string to clients' development, taking themselves along for a ride, which depends upon someone else's motivation. This, of course, brings up many issues regarding boundaries between clinician and client. A clinician does not want to be at the mercy of the client; this might cause ripples to be felt throughout that therapist's whole practice. The opposite end is where the emotionally cut-off clinician practices - a place that does not necessarily engender good therapy and creates (possible on purpose on some level) no emotional connection or attachment with the clinician. This, just like the opposite end, can lead to echoes into other therapy sessions. So what does the middle look like? And why am I so afraid of the extremes? And how have I seen myself going into either extreme?
Betwixt these two extremes, a clinician finds the land of emotional interest without emotional investment or dependence. This is a space where the clinician is comfortable with being present and appropriately emotional/empathetic with the client without allowing his or her personal life to bleed through into the session (non-therapeutically). To some degree, I think that it takes time to find this balance.