Time is limited and expensive in session. So Beyond basic courtesy, a T's Self disclosure should be limited and only relevant to the topic at hand, i.e. YOU. A therapist should never be telling you stories or any personal anecdotes that make you focus on the Therapist. It should only be used as a tool to help you deal with your own stuff.

My T doesn't disclose much at all about herself and when she does it's in response to what I'm talking about and only to validate or normalize my own situation. The most personal stuff she's ever said was very thought out and carefully disclosed and she checked with me to make sure it was the right thing to do. It was useful for me to hear her experience in that it helped me realize something about myself. (i.e., I'm not the only one who's felt this way or had this thing happen, etc.)