I'm glad Sandi was straight with you. It is what you've been told...she is doing what she thinks is the right thing for her and will continue to do that. By working on yourself and dropping the anger issue, you are giving her something to consider in terms of options. I would say go to the mediation and go through it with the understanding that this is the real deal...you are working your way towards divorce. Dragging your feet or putting your head in the sand doesn't change reality. The reality (at the moment) is that she's sure she wants a divorce. Going to this and being a mature, confident, and yes happy (not angry, vindictive, and blaming) will let her see that you want to work on your issues. If you can't go without throwing out blame and guilt, then don't bother.
In the end, it's not the years in your life that count. It's the life in your years. Abraham Lincoln
It is hard to fail, but it is worse never to have tried to succeed. Theodore Roosevelt
