You know, sometimes I think that healing from this kind of loss can really take a long time. I don't know a lot about your sitch, but 12 years is a long time together. Feeling down does feel crappy. But far more important than some healing timeline is to be thinking about small steps you can do for you today...just like you posted about going for a walk!
I wish there were things other than distraction sometimes to heal the broken heart.