TANYA CHAPTER 27: Part Five "Get Shorty" How spiritual shortcomings were specifically designed for Divine satisfaction.
TANYA: CHAPTER 28 Part Two "Focus on Davening: Why mind-wandering weirdness during Davening actually proves nothing!
TANYA CHAPTER 18: PART ONE http://www.chabad.org/library/tanya/tanya_cdo/aid/7897/jewish/Chapter-18.htm