Hey Ruth,

Great news...going back is scary.  Every step causes some worry.  Use the Pfitz work-out and stick to it is all I can say.  The schedule starts out with walk-runs which are more walking than running.  It gradually builds up to running.  After first few weeks you may be tempted to skip as you run more but I would recommend sticking it out till end of schedule.  I also learned after Pfitz all the training errors I was doing. 

Now I try to keep to a schedule with rest days [for cross training] and varying types of runs -even when not training for a race.   I also observe the 10% weekly mileage rule as well  with fall back weeks in mileage.  In addition, I always try  to stretch afterwards since muscles in leg can affect how the foot lands and pushes off and vice versa.  I also retired the shoes/type that I was wearing when SF happenned.   

Good luck!