Hawzah News Agency – The merciful prophet of Islam (pbuh) says:

إنّ الشَّديدَ لَيسَ مَن غَلَبَ النّاسَ، ولكِنَّ الشَّديدَ مَن غَلَبَ على‏ نَفسِهِ.

'A strong person is not one who overcomes people, but a strong person is one who overcomes his own self.'

Source: Tanbih al-Khawatir, v. 2, p. 10