You are right not to beat yourself up over it. The WAW script is that they have some point pre-defined when they will make their escape. Right up until that point, the LBS has no idea that there is a problem, in fact, the M can actually be very good! The W usually doesn't nag, the sex life might even be just fine, right up until the trigger event occurs and they walk.
In my W's case, the trigger was when she found the OM, as is a very common case with WAWs, but it can also be when they complete their education, when the kids are old enough, when they can support themselves, etc. It would be nice if us LBHs would have some warning that this is going on, but usually there is none.
With the magic ability of hindsight, it becomes a little clearer what we should have been doing, and how selfish, inattentive, unloving, or uncaring we were. Unfortunately for us, by the time they are on their way out the door, the things that they are complaining about and issues that they use to bash us are "unfixable". Trying to fix them after-the-fact just leads to resentment, and justifies their behavior in their mind. This is why detachment, and GAL are so important. Just GAL can be seen as appeasement or even pursuit if it is done purely for the purpose of wooing a wayward W back. Of course you want you W back, that IS the purpose of DB'ing, right? Well, maybe. I think DB'ing has a higher purpose. for me, it is about becoming a better person and forging stronger ties to our kids and building a stronger, more loving family unit. If the WAS wants to be part of what you are building for your family, then you get the collateral benefit of getting your W back and forging a new marriage with the old people (like DrHemlock just said!). If they do move on, then you have the strength and foundation for a good life without them.
Honestly, where I am in my sitch, it doesn't really matter to me if my W comes back or not. Of course I still love her, and of course if she did come back with the expressed purpose of re-building our marriage I would take her back, but it doesn't matter to me if that actually happens because I know I will be happy with or without her.
Me40 WAW37 M18 T20 S18,14 D13 EA Bomb 6/08 Sep 11/20/08 Ret 08/09 Sep/Filed 11/09