I didn't sit my husband down and drop a bomb so much as I spilled my guts one day after about a week of sitting on how I would tell him that I needed to open the marriage. Another man (whom I met in the PTA) had begun to show interest in me and in the beginning, I chuckled about this with my husband. He and I always had an emotional intimacy and so including him on the fun was just part of an overall closeness that we shared. I figured it was a passing flirtation, but the mutual feelings blossomed. I had always been open to the concept of a non-monogamous marriage, but my conservative husband would affectionately laugh at the thought. Very soon after the mutual feelings developed with PTA Dad, my husband sensed something was different and he asked me about it. That's when I had a difficult talk with him about my need for us to seriously consider poly. I don't know how people cheat because for me, it wasn't physically possible to sit on this secret for very long - maybe it was a week. I wasn't driven by guilt or ethics or anything other than I just couldn't contain such a secret. It didn't fit at all with the kind of relationship that my husband and I had - and though he didn't have words until we talked about it, he could feel that something was very different.
We bumbled our way through a year of poly, but ultimately it was not something that fit with our relationship. Of course, he had feelings of anger, but not really betrayal because he could see how my wanting additional partners was an extension of who he'd always known me to be - the experimental, questioning traveler. Likewise, I owned up to having chosen a conservative, ultra stable tenured college professor as my mate. Neither of us blamed the other for being who we'd always been and as we worked our way toward what was once unthinkable - separation - we did it with care. He did feel angry for a few months, but I didn't sink into guilt and instead let him have his distance. I think that anger is part of intimacy at times, as is fear and other negative emotions, but in a genuinely intimate relationship these feelings move through fairly quickly. Even as we were separating - and some days it was painfully so - we were intimately connected. It's no surprise to me that my husband found a wonderful new parter soon after moving out. She is a lovely woman and much better suited to his monogamous, stable, traditional preferences. My husband was an enormous stabilizing presence that I needed for creating a family, but I was never a "plant my flag forever" kind of person and when I suggested poly in our marriage, part of him was angry for sure but the bigger part of him was not surprised at all.
We're almost officially uncoupled now and ours is by far the happiest divorce I know. He's over here almost every day that he is not with his GF, who lives about five hours away. Many days, our kids are off doing their own things and it's him and me hanging out with the dogs. He's had his own place during the separation, but we kept the kids here and didn't do the typical "dad's place/mom's place" back and forth. The initial plan was for me to let him have his time here with them while I overnighted in his apartment, but my leaving the house during his visits was never really necessary. His GF has been here a few times, once for Thanksgiving, and it's not a breeze for me having her here, but my husband and I talk about it and are finding our way. I've dated this whole time and he's gotten to the point where he gives me very helpful relationship advice. We've even given feedback about the experience of being married to the other, which is enormously helpful going forward in our subsequent relationships.
So, yeah, there have been some mammoth changes and some pretty intense feelings, but no, none of this came out of the blue.