The honorable thing to do if you're in a marriage that isn't working is to leave it/tell your partner it is over BEFORE you start up with someone else. I know divorces take forever in the west, and I don't mean you can't date/do anything until it's all finalized, but it IS rather bad behavior to be actively courting someone else when you're still living with your spouse, not having told them that you're no longer interested in continuing the relationship.

"Marriage is a wonderful institution...but who wants to live in an institution?" -- Groucho Marx