All you can do is start with yourself. Begin working towards making a better YOU. Start reading, go to therapy, learn as much as possible about relationships and marriage, and what makes them great. Join a gym, make friends, take classes, do things you love..... You may not be able to save your marriage, but if you focus on yourself and creating a much healther you, whatever realtionships you have in the future will be much better.
You can't control your wife or change her. Staying or leaving will have to be her choice and you'll need to accept that. But making yourself someone emotionally healthy, independent, happy, stable, etc... will make you the more attractive option (for either your wife or someone else in the future).
When (or if?) you do talk with your wife be friendly, smile and give her LOTS of space. Do not have any expectations, no negative words, blame, etc... just be a great listener and be a distant FRIEND.
There is no arriving, ever. It is all a continual becoming.
