MBF, which book do you have - Divorce Busting or Divorce Remedy? "Remedy" has more practical advice.
two points: 1) Michele talks about how, at the beginning, you have to let yourself feel the pain; the only way out is to go through it. it is like a grieving process. 2) afterwards, you can use "thought stopping", where you train yourself to stop thinking the negative painful thoughts.
good luck and keep us posted about your progress! we are here for you.