Cut To The Quick Meaning

Example: Used other than as an idiom: see cut,‎ quick.
To hurt a person deeply, especially emotionally.
1902, Joseph Conrad, Heart of Darkness,
  I was cut to the quick at the idea of having lost the inestimable privilege of listening to the gifted Kurtz.
1960, P. G. Wodehouse, Jeeves in the Offing, chapter XI:
  But you must remember that we were boys together, and a fellow naturally confides in a chap he was boys together with. Anyway, be that as it may, he poured out his soul to me, and he hadn't been pouring long before I was able to see that he was cut to the quick. His blood pressure was high, his eye rolled in what they call a fine frenzy, and he was death-where-is-thy-sting-ing like nobody's business.
To get to the most essential idea or point.
2005, Cristina Malcolmson, "Review of Fantasies of Female Evil: The Dynamics of Gender and Power in Shakespearean Tragedy by Cristina Alfar", Shakespeare Quarterly, vol. 56, no. 1, p. 112,
  Alfar's analysis cuts to the quick of the socioeconomic structures that underlie marriage, primogeniture, monarchy, and imperialism.