Well, for me, I started posting a lot. It was a way to help process what I was going through, and a way to offer support, even if it was only "I hear you" types of things. I branched out slowly, sorta feeling my way, because I could get so empathically drawn-into someone else's pain. I read A LOT on other forums before I went there. I had to be comfortable before I felt free to post.
And I step away, at times. If I'm really hurting, I limit myself. It's the oxygen-bag drill. I have to take care of myself first. If I felt myself getting too engaged, or too enraged, or too depressed, I'd back away. Because I know that I brought some of those feelings back into my relationship. Most of the time, it caused an increased need for me to check up on my FWH.
Those times are getting, far, far less now. I think that once you start healing a bit and it's not so raw, you can start to distance yourself from the pain leakage. Sort of like how you de-sensitize yourself from triggers. There are many times when I'd like to be a fist popping out of cell phone, bopping some jackass of a WS upside the head, but I don't bring it home to my FWH anymore.