I think that the choice of who to tell is absolutely critical as many of you have said. We need to choose wisely, and plan what we're going to say, and have given some sort of consideration to how the other person is likely to react, because this information can be very confronting and distressing to certain others, particularly if it comes out of the blue. Not to say that we're responsible for managing others' reactions, but I do think we have some responsibility to consider the other person's welfare as well.
Choosing unwisely and trusting this information to the wrong person can be an unspeakable setback... trust me, I know. Thankfully, choosing wisely and having a positive experience can be enormously validating,and a huge relief, even if a conflicted one.
In my case, it became necessary for me to provide an explanation to my new manager. My work performance and general behaviour at work are being significantly impacted right now and obviously he was entitled to an explanation. He knew I was seeing T and had some vague knowledge of some peripheral issues, but in order that we make some appropriate arrangements for my work environment, it was the right and necessary choice. We then had a lot of very careful and sensitive discussion about who else needed to know what, and some other partial disclosures were made to key others.
Currently it's all still very raw for me, very painful and almost too confronting. But I also know rationally that it was the right thing and will probably help the workplace remain a stable and safe place for me in the short term. Humble pie tastes sour and it burns like hell, but I know it's for the best.
Maddog