From the Jung book I'm reading on my subway rides (emphasis mine):

We should expect the doctor of have an infleunce on the patient in every effective psychic treatment: but this influence can only take place when he too is affected by the patient. You can exert no influence if you are not susceptible to influence.

This is a pretty deep thing, and it goes well outside psychotherapy. It's something I wrestled with a lot when I was more regularly into acting and performing. Creating a space of vulnerability on stage was a critical part of the method that I pursued. This involves breaking the fourth wall, bringing the audience into direct human contact with the performer. It's a powerful technique that only works at close-range, but I really enjoyed using it.

This is also something that I have to work on in my personal life. In spite of my gregarious nature, I keep a pretty sizable portion of myself to myself in most situations, or at least immune to external input. That's a limitation, maybe borne from defense (once bitten, etc), that I'd like to work out.