Complex sentence: For decades afterward, Jennings repeatedly admitted that he felt responsible for the crash that killed Buddy Holly; this profoundly misplaced sense of guilt precipitated bouts of substance abuse through much of Jennings' career.
Split into simpler sentences: For decades afterward, Jennings repeatedly admitted that he felt responsible for the crash that killed Buddy Holly. This sense of guilt precipitated bouts of substance abuse through much of Jennings' career.