Srimad Bhagavatam Canto 10, Chapter 04, Text 38

SB 10.4.38

yathamayo ’nge samupeksito nrbhir
 na sakyate rudha-padas cikitsitum
yathendriya-grama upeksitas tatha
 ripur mahan baddha-balo na calyate
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
As a disease, if initially neglected, becomes acute and impossible to cure, or as the senses, if not controlled at first, are impossible to control later, an enemy, if neglected in the beginning, later becomes insurmountable.
Srimad Bhagavatam Canto 10, Chapter 04, Text 37
Srimad Bhagavatam Canto 10, Chapter 04, Text 39