Ramayana
शक्तस्त्वमात्मना ऽ ऽत्मानं विनेतुं मनसैव हि । लोकान्सर्वांश्च काकुत्स्थ किं पुनः शोकमात्मनः ॥ 7-52-13 ॥
"You are able by your own mind alone to discipline yourself, and indeed all the worlds, O Kakutstha; how much more, then, the grief of your own self?"
english translation