Harrier, I'd like to give my two cents too, as my situation has evolved to the Piecing stage. One of the more helpful DB tools I used when my W and I were in our roommate phase, was GAL. My only other option was probably D, but I wasn't ready to take that step.
I went out and took ballroom dancing lessons on my own, when my W went on-strike and refused to attend any further classes with me. I found venues to practice my dancing and became connected in the ballroom community. I was attracted to and women were attracted to me, which reminded me that I could be attractive. I didn't pursue anything, of course, but had a social network to turn to if we went our separate ways. It kept my mind focused on something constructive, and allowed me to grow in ways I needed to. In time, my W showed interest in wanting to join me. I let her, even though it was awkward, and I was ambivalent about the R.
It is an emotional time for you, and there's no way to make it easier, but you can make it more difficult. You're looking for reassurance from a W who can't provide it at this time. You will need to find the courage to face and accept things as they are. You will need to find a way to slow down and live more in the present. You're spending too much time and giving too much weight to thinking. Do you have a spiritual or religious practice? I'm a fan and promoter of meditation. Running can be your meditation.
I'm glad that you're getting advice on DB technique, because making small changes from the same patterns can take you down a more constructive path. For me it was joining a meditation group when my W and I separated in 04'. I still meditate to this day. The other one was taking ballroom dance lessons (09') and going out on my own to dance, and networking in the local dance community. It allowed me to grow in different ways and created a buffer from my problems.
CL
CL 53 W 54 M 20 yrs. 03'-09' Separation + Old Patterns + GAL 10-14' Piecing
"The Master allows things to happen. She shapes events as they come."