Hindsight is 20/20, don't beat yourself up. You were together for 11 years. In that time, without concerted effort, things *will* get on "auto-pilot" in your relationship, and that's not a problem provided that both of you are comfortable and getting your needs met.
The problem with autopilot is that sudden attention from someone new looks so much better by comparison. "Hey, this new person is paying all this attention to me and telling me I'm great, while my spouse never pays attention to me." I think that's kind of where it starts. Now to be fair, the WAS tends not to think about the fact that they are ALSO on autopilot and not paying attention to the other person either. You need to make deposits in the love bank if you expect to take withdrawals.
It's healthy to understand your W's complaints about you, the dynamics that drew you apart, and to make changes for yourself to be a better spouse or partner in the future. It is not healthy to deconstruct everything that's happened and shoulder the blame for it. If you feel you neglected her, she neglected you too in all likelihood. If you complained about her late hours, it's probably because you weren't getting the attention you wanted. Those things are not your fault.
At some point, your W chose to cross the line, and you are not responsible for that. You SHARE responsibility for letting your relationship erode to a point that you were both vulnerable, but she is solely responsible for taking the actions she did. That does NOT reflect poorly on you, and you are not to blame for it.
Accuray
Married 18, Together 20, Now Divorced M: 48, W: 50, D: 18, S: 16, D: 12 Bomb Dropped (EA, D): 7/13/11 Start Reconcile: 8/15/11 Bomb Dropped (EA, D): 5/1/2014 (Divorced) In a New Relationship: 3/2015