The human body is a remarkable machine. It will take all sorts of abuse and, with the right rest and treatment, recover 100% over time.
If you notice discomfort of the type you describe, then rest until it goes away and begin the exercises again. It’s generally not the exercises, but your enthusiasm that causes the discomfort and minor pain.
As with any physical exercise routine, rest is the unspoken third factor, behind exercise and diet.
Began December 2009 at 5 7/8" length and 5" girth.
As of December 5th 2012 7 3/8" BPEL and 6 1/8" base girth.
Going for the magic 8"x6"