Zen,
Thanks for this! I've asked at least three people for information along these lines just in the last few days, and none of them have been able to give me any really clear guidelines, telling me that it comes down to a judgement call. What my T said about it was helpful, but not clear-cut at all.
My question was about self-disclosure in a professional setting. I have a Head Start parent I am trying to work with, who has been hesitant (or outright refusing) to talk to us or accept services for her daughter. She feels like she is being judged and people keep telling her all these things that she isn't doing well enough. When I told her that I had been there and felt like that too, she agreed to meet with me. Now I'm wondering where to draw the line in terms of further self-disclosure should it come up. Lately, my boundaries have tended to be too loose, so I've been worried about the possibility of disclosing too much, and have been looking for a rule or something so that I can avoid crossing the line. What my T told me (and she also applied it to her relationship with me) was that it's ok to self-disclose if a client asks a direct question and you are comfortable answering it, and it serves some purpose that is helpful to the client (not shifting the focus away from the client in order to tell one's own stories).
With friends (or on message boards like this one) it's different, since it is a mutually supportive relationship, not a unidirectional one, so turn-taking is appropriate. Still, a lot of this information can be applied. It does get confusing knowing where to set healthy boundaries here, since sometimes we are helping others and other times we are asking for help, and we are all members of this group, not therapists. I try to keep in mind what the objective is when I post here, whether it is to ask for help or to support someone else, but still, I think that self-disclosure is more appropriate here than it would be in a professional relationship, and I'll tell my own experiences quite a lot. It does seem to help to know that someone else has been through similar things sometimes. I hope so anyway, since pretty much all of my secrets are here somewhere if anyone wants to find them and read them.

But I still need to watch out for using my replies to others as a way to ask for help for myself. My apologies for that.
You know, I always thought that I tended to have boundaries that were too tight, and I have loosened them considerably in the last couple of years, but I have realized that my boundaries have probably always tended more towards too loose than too tight.
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“We should always pray for help, but we should always listen for inspiration and impression to proceed in ways different from those we may have thought of.”
– John H. Groberg