Astanga Hrudaya
मर्माभिघातः स्वल्पोऽपि प्रायशो बाधतेतराम् । रोगा मर्माश्रयास्तद्वत्प्रक्रान्ता यत्नतोऽपि च ॥ ७० ॥
Importance of Marmas: Injury to vital spots, though slight (mild) usually produces serve pain (trouble); so also the diseases which are localised in the vital spots (do not get cured) in spite of great effort in treating it.
english translation