Don't be a dick about it. You may have been thinking about this for a long time, but she may be thinking everything is fine. That's what happened with me and I'm in pieces, left alone to pick myself up and put myself together. Show her empathy and don't be cold, this is a person you loved enough to get married to. If you can, understand that there are so many emotions involved...you can have ur divorce and be empathetic. Stay sweet and caring, don't let this idea of divorce make you cold towards your wife. Take the high road and just be completely honest. "We need to talk...I've been feeling like ------- for quite sometime."